/*
  Racket
  Copyright (c) 2004-2014 PLT Design Inc.
  Copyright (c) 2000-2001 Matthew Flatt

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301 USA.

  libscheme
  Copyright (c) 1994 Brent Benson
  All rights reserved.
*/

/* This file implements the TCP and UDP interfaces. */

#include "schpriv.h"
#include <ctype.h>

#ifndef NO_TCP_SUPPORT
#ifdef USE_TCP

#ifdef UNISTD_INCLUDE
# include <unistd.h>
#endif
#ifdef USE_ULIMIT
# include <ulimit.h>
#endif
#ifdef FILES_HAVE_FDS
# include <sys/types.h>
# include <sys/time.h>
# ifdef BSTRING_INCLUDE
#  include <bstring.h>
# endif
# ifdef SELECT_INCLUDE
#  include <sys/select.h>
# endif
# ifdef HAVE_POLL_SYSCALL
#  include <poll.h>
# endif
#endif
#ifdef IO_INCLUDE
# include <io.h>
#endif
#ifdef INCLUDE_OSKIT_SOCKET
# include <oskit/net/socket.h>
#endif
#ifdef NO_ERRNO_GLOBAL
static int mzerrno = 0;
# define errno mzerrno
#else
# include <errno.h>
#endif

#ifdef USE_UNIX_SOCKETS_TCP
# include <netinet/in.h>
# include <netdb.h>
# include <sys/socket.h>
# include <fcntl.h>
# define TCP_SOCKSENDBUF_SIZE 32768
# define NOT_WINSOCK(x) x
# define SOCK_ERRNO() errno
# define WAS_EAGAIN(e) ((e == EWOULDBLOCK) || (e == EAGAIN) || (e == EINPROGRESS) || (e == EALREADY))
# define WAS_WSAEMSGSIZE(e) 0
# define mz_AFNOSUPPORT EAFNOSUPPORT
#endif

#ifdef USE_WINSOCK_TCP
# include <process.h>
# include <winsock2.h>
# include <ws2tcpip.h>
# ifndef __MINGW32__
#  include <wspiapi.h>
# else
typedef int (WINAPI*gai_t)(const char*, const char*, const struct mz_addrinfo *, struct mz_addrinfo **);
typedef void (WINAPI*fai_t)(struct mz_addrinfo *ai);
# endif
struct SOCKADDR_IN {
  short sin_family;
  unsigned short sin_port;
  struct in_addr sin_addr;
  char sin_zero[8];
};
# define NOT_WINSOCK(x) 0
# define SOCK_ERRNO() WSAGetLastError()
# define WAS_EAGAIN(e) ((e == WSAEWOULDBLOCK) || (e == WSAEINPROGRESS))
# define WAS_WSAEMSGSIZE(e) (e == WSAEMSGSIZE)
# define mz_AFNOSUPPORT WSAEAFNOSUPPORT
extern int scheme_stupid_windows_machine;
# ifdef MZ_USE_PLACES
static HANDLE winsock_sema;
# endif
#endif

intptr_t scheme_socket_errno() {
  return SOCK_ERRNO();
}

#include "schfd.h"

#define TCP_BUFFER_SIZE 4096

#ifdef USE_UNIX_SOCKETS_TCP
typedef intptr_t tcp_t;
# define INVALID_SOCKET (-1)
static void closesocket(intptr_t s) {
  int cr;
  do { 
    cr = close(s);
  } while ((cr == -1) && (errno == EINTR));
}
#endif

#ifdef USE_WINSOCK_TCP
typedef SOCKET tcp_t;
#endif

#ifdef USE_SOCKETS_TCP
typedef struct {
  Scheme_Object so;
  Scheme_Custodian_Reference *mref;
  int count;
# ifdef HAVE_POLL_SYSCALL
  struct pollfd *pfd;
# endif
  tcp_t s[mzFLEX_ARRAY_DECL];
} listener_t;
#endif

typedef struct Scheme_Tcp_Buf {
  MZTAG_IF_REQUIRED
  short refcount;
  char *buffer, *out_buffer;
  short bufpos, bufmax;
  short hiteof, bufmode;
  short out_bufpos, out_bufmax;
  short out_bufmode;
} Scheme_Tcp_Buf;

typedef struct Scheme_Tcp {
  Scheme_Tcp_Buf b;
  tcp_t tcp;
  int flags;
} Scheme_Tcp;

# define MZ_TCP_ABANDON_OUTPUT 0x1
# define MZ_TCP_ABANDON_INPUT  0x2

#define UDP_IS_SUPPORTED

#ifdef UDP_IS_SUPPORTED

typedef struct Scheme_UDP {
  Scheme_Object so; /* scheme_udp_type */
  MZ_HASH_KEY_EX
  tcp_t s; /* ok, tcp_t was a bad name */
  char bound, connected;
  Scheme_Object *previous_from_addr;
  Scheme_Custodian_Reference *mref;
} Scheme_UDP;

#endif /* UDP_IS_SUPPORTED */

#endif /* USE_TCP */

#if defined(WINDOWS_PROCESSES) || defined(WINDOWS_FILE_HANDLES)
# define DECL_OS_FDSET(n) fd_set n[1]
# define INIT_DECL_OS_FDSET(r, w, e) /* empty */
# define INIT_DECL_OS_RD_FDSET(r) /* empty */
# define INIT_DECL_OS_WR_FDSET(r) /* empty */
# define INIT_DECL_OS_ER_FDSET(r) /* empty */
# define MZ_OS_FD_ZERO(p) FD_ZERO(p)
# define MZ_OS_FD_SET(n, p) FD_SET(n, p)
# define MZ_OS_FD_CLR(n, p) FD_CLR(n, p)
#else
# define DECL_OS_FDSET(n) DECL_FDSET(n, 1)
# define INIT_DECL_OS_FDSET(r, w, e) INIT_DECL_FDSET(r, w, e)
# define INIT_DECL_OS_RD_FDSET(r) INIT_DECL_RD_FDSET(r)
# define INIT_DECL_OS_WR_FDSET(r) INIT_DECL_WR_FDSET(r)
# define INIT_DECL_OS_ER_FDSET(r) INIT_DECL_ER_FDSET(r)
# define MZ_OS_FD_ZERO(p) MZ_FD_ZERO(p)
# define MZ_OS_FD_SET(n, p) MZ_FD_SET(n, p)
# define MZ_OS_FD_CLR(n, p) MZ_FD_CLR(n, p)
#endif
#define MZ_OS_FD_ISSET(n, p) FD_ISSET(n, p)

static Scheme_Object *tcp_connect(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_connect_break(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_listen(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_stop(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_accept_ready(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_accept(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_accept_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_accept_break(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_listener_p(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_addresses(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_abandon_port(int argc, Scheme_Object *argv[]);
static Scheme_Object *tcp_port_p(int argc, Scheme_Object *argv[]);

static Scheme_Object *make_udp(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_close(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_p(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_bound_p(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_connected_p(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_bind(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_connect(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send_to(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send_to_star(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send_star(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send_to_enable_break(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_send_enable_break(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_receive(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_receive_star(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_receive_enable_break(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_read_ready_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_write_ready_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_read_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_write_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_write_to_evt(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_loopback_p(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_set_loopback(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_ttl(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_set_ttl(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_interface(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_set_interface(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_join_group(int argc, Scheme_Object *argv[]);
static Scheme_Object *udp_multicast_leave_group(int argc, Scheme_Object *argv[]);

static int tcp_check_accept_evt(Scheme_Object *ae, Scheme_Schedule_Info *sinfo);
static void tcp_accept_evt_needs_wakeup(Scheme_Object *_ae, void *fds);
#ifdef UDP_IS_SUPPORTED
static int udp_evt_check_ready(Scheme_Object *uw, Scheme_Schedule_Info *sinfo);
static void udp_evt_needs_wakeup(Scheme_Object *_uw, void *fds);
#endif

#ifdef MZ_PRECISE_GC
static void register_traversers(void);
#endif

void scheme_init_network(Scheme_Env *env)
{
  Scheme_Env *netenv;

#ifdef MZ_PRECISE_GC
  register_traversers();
#endif

  netenv = scheme_primitive_module(scheme_intern_symbol("#%network"), env);

  GLOBAL_PRIM_W_ARITY2 ( "tcp-connect"               , tcp_connect              , 2 , 4 , 2 , 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY2 ( "tcp-connect/enable-break"  , tcp_connect_break        , 2 , 4 , 2 , 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "tcp-listen"                , tcp_listen               , 1 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "tcp-close"                 , tcp_stop                 , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "tcp-accept-ready?"         , tcp_accept_ready         , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY2 ( "tcp-accept"                , tcp_accept               , 1 , 1 , 2 , 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "tcp-accept-evt"            , tcp_accept_evt           , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY2 ( "tcp-accept/enable-break"   , tcp_accept_break         , 1 , 1 , 2 , 2 , netenv ) ;
  GLOBAL_FOLDING_PRIM  ( "tcp-listener?"             , tcp_listener_p           , 1 , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY2 ( "tcp-addresses"             , tcp_addresses            , 1 , 2 , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "tcp-abandon-port"          , tcp_abandon_port         , 1 , 1 , netenv ) ;
  GLOBAL_FOLDING_PRIM  ( "tcp-port?"                 , tcp_port_p               , 1 , 1 , 1 , netenv ) ;

  GLOBAL_PRIM_W_ARITY  ( "udp-open-socket"           , make_udp                 , 0 , 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-close"                 , udp_close                , 1 , 1 , netenv ) ;
  GLOBAL_FOLDING_PRIM  ( "udp?"                      , udp_p                    , 1 , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-bound?"                , udp_bound_p              , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-connected?"            , udp_connected_p          , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-bind!"                 , udp_bind                 , 3 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-connect!"              , udp_connect              , 3 , 3 , netenv ) ;

  GLOBAL_PRIM_W_ARITY  ( "udp-send-to"               , udp_send_to              , 4 , 6 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send"                  , udp_send                 , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send-to*"              , udp_send_to_star         , 4 , 6 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send*"                 , udp_send_star            , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send-to/enable-break"  , udp_send_to_enable_break , 4 , 6 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send/enable-break"     , udp_send_enable_break    , 2 , 4 , netenv ) ;

  GLOBAL_PRIM_W_ARITY  ( "udp-receive!"              , udp_receive              , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-receive!*"             , udp_receive_star         , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-receive!/enable-break" , udp_receive_enable_break , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-receive-ready-evt"     , udp_read_ready_evt       , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send-ready-evt"        , udp_write_ready_evt      , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-receive!-evt"          , udp_read_evt             , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send-evt"              , udp_write_evt            , 2 , 4 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-send-to-evt"           , udp_write_to_evt         , 4 , 6 , netenv ) ;

  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-loopback?"   , udp_multicast_loopback_p , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-set-loopback!", udp_multicast_set_loopback,2, 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-ttl"         , udp_multicast_ttl        , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-set-ttl!"    , udp_multicast_set_ttl    , 2 , 2 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-interface"   , udp_multicast_interface  , 1 , 1 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-set-interface!", udp_multicast_set_interface,2,2, netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-join-group!" , udp_multicast_join_group , 3 , 3 , netenv ) ;
  GLOBAL_PRIM_W_ARITY  ( "udp-multicast-leave-group!", udp_multicast_leave_group, 3 , 3 , netenv ) ;

  scheme_finish_primitive_module(netenv);

#ifdef USE_WINSOCK_TCP
# ifdef MZ_USE_PLACES
  if (!winsock_sema) {
    winsock_sema = CreateSemaphore(NULL, 1, 1, NULL);
  }
# endif
#endif
}

static int check_fd_sema(tcp_t s, int mode, Scheme_Schedule_Info *sinfo, Scheme_Object *orig)
{
  Scheme_Object *sema;

  sema = scheme_fd_to_semaphore(s, mode, 1);
  
  if (sema) {
    if (!scheme_wait_sema(sema, 1)) {
      if (sinfo && !sinfo->no_redirect)
        scheme_set_sync_target(sinfo, sema, orig, NULL, 0, 0, NULL);
      return 0;
    }
  }

  return 1;
}

/*========================================================================*/
/*                             TCP glue                                   */
/*========================================================================*/


/* These two need o be outside of USE_TCP */
#define PORT_ID_TYPE "(integer-in 1 65535)"
#define CHECK_PORT_ID(obj) (SCHEME_INTP(obj) && (SCHEME_INT_VAL(obj) >= 1) && (SCHEME_INT_VAL(obj) <= 65535))
#define LISTEN_PORT_ID_TYPE "(integer-in 0 65535)"
#define CHECK_LISTEN_PORT_ID(obj) (SCHEME_INTP(obj) && (SCHEME_INT_VAL(obj) >= 0) && (SCHEME_INT_VAL(obj) <= 65535))

#ifdef USE_TCP

#ifdef USE_SOCKETS_TCP
#define MAKE_TCP_ARG tcp_t tcp, 
#else
#define MAKE_TCP_ARG
#endif

#define REGISTER_SOCKET(s) /**/
#define UNREGISTER_SOCKET(s) /**/

#ifdef USE_UNIX_SOCKETS_TCP
typedef struct sockaddr_in mz_unspec_address;
#endif
#ifdef USE_WINSOCK_TCP
typedef struct SOCKADDR_IN mz_unspec_address;
# undef REGISTER_SOCKET
# undef UNREGISTER_SOCKET
# define REGISTER_SOCKET(s) winsock_remember(s)
# define UNREGISTER_SOCKET(s) winsock_forget(s)
#endif

/******************************* hostnames ************************************/

#if defined(OS_X) || defined(USE_PTHREAD_THREAD_TIMER)
# define PTHREADS_OK_FOR_GHBN
#endif

# ifdef PROTOENT_IS_INT
#  define PROTO_P_PROTO PROTOENT_IS_INT
# else
SHARED_OK static struct protoent *proto;
#  define PROTO_P_PROTO (proto ? proto->p_proto : 0)
# endif

# ifndef MZ_PF_INET
#  define MZ_PF_INET PF_INET
# endif

/* For getting connection names: */
#define MZ_SOCK_NAME_MAX_LEN 256
#define MZ_SOCK_HOST_NAME_MAX_LEN 64
#define MZ_SOCK_SVC_NAME_MAX_LEN 32

/* mz_addrinfo is defined in scheme.h */

#ifdef HAVE_GETADDRINFO
# define mzAI_PASSIVE AI_PASSIVE 
# define mz_getaddrinfo getaddrinfo
# define mz_freeaddrinfo freeaddrinfo
# define mz_gai_strerror gai_strerror
#else
# define mzAI_PASSIVE 0
static int mz_getaddrinfo(const char *nodename, const char *servname,
			  const struct mz_addrinfo *hints, struct mz_addrinfo **res)
  XFORM_SKIP_PROC
{
  struct hostent *h;

#ifdef __MINGW32__
  {
    HMODULE hm;
    hm = LoadLibrary("ws2_32.dll");
    if (hm) {
      gai_t gai;
      gai = (gai_t)GetProcAddress(hm, "getaddrinfo");
      if (gai) {
	int v;
	v = gai(nodename, servname, hints, res);
	if (!v && !(*res)->ai_addr)
	  (*res)->ai_addrlen = 0;
	return v;
      }
    }
  }
#endif

  if (nodename)
    h = gethostbyname(nodename);
  else
    h = NULL;

  if (h || !nodename) {
    GC_CAN_IGNORE struct mz_addrinfo *ai;
    GC_CAN_IGNORE struct sockaddr_in *sa;
    int j, id = 0;

    ai = (struct mz_addrinfo *)malloc(sizeof(struct mz_addrinfo));
    sa = (struct sockaddr_in *)malloc(sizeof(struct sockaddr_in));
    ai->ai_addr = (struct sockaddr *)sa;

    ai->ai_addrlen = sizeof(struct sockaddr_in);
    if (servname) {
      for (j = 0; servname[j]; j++) {
	id = (id * 10) + (servname[j] - '0');
      }
    }

    ai->ai_family = MZ_PF_INET;
    ai->ai_socktype = hints->ai_socktype;
    ai->ai_protocol = hints->ai_protocol;
    ai->ai_next = NULL;

    sa->sin_family = (id ? AF_INET : AF_UNSPEC);
    j = htons(id);
    sa->sin_port = j;
    memset(&(sa->sin_addr), 0, sizeof(sa->sin_addr));
    memset(&(sa->sin_zero), 0, sizeof(sa->sin_zero));
    if (h)
      memcpy(&sa->sin_addr, h->h_addr_list[0], h->h_length); 
    
    *res = ai;
    return 0;
  }
  return h_errno;
}
void mz_freeaddrinfo(struct mz_addrinfo *ai)
  XFORM_SKIP_PROC
{
#ifdef __MINGW32__
  {
    HMODULE hm;
    hm = LoadLibrary("ws2_32.dll");
    if (hm) {
      fai_t fai;
      fai = (fai_t)GetProcAddress(hm, "freeaddrinfo");
      if (fai) {
	fai(ai);
	return;
      }
    }
  }
#endif

  free(ai->ai_addr);
  free(ai);
}
const char *mz_gai_strerror(int ecode)
  XFORM_SKIP_PROC
{
#ifdef __MINGW32__
  return NULL; /* => use FormatMessageW(), instead */
#else
  return hstrerror(ecode);
#endif
}
#endif

#if defined(USE_WINSOCK_TCP) || defined(PTHREADS_OK_FOR_GHBN)

# ifdef USE_WINSOCK_TCP
#  ifdef __BORLANDC__
#   define MZ_LPTHREAD_START_ROUTINE unsigned int (__stdcall*)(void*)
#  else
#   define MZ_LPTHREAD_START_ROUTINE LPTHREAD_START_ROUTINE
#  endif
# else
#  include <pthread.h>
#   define MZ_LPTHREAD_START_ROUTINE void *(*)(void *)
# endif

typedef struct {
# ifdef USE_WINSOCK_TCP
  HANDLE th;
# else
  int pin;
# endif
  struct mz_addrinfo *result;
  int err;
  int done;
} GHBN_Rec;

/* For in-thread DNS: */
#define MZ_MAX_HOSTNAME_LEN 128
#define MZ_MAX_SERVNAME_LEN 32

typedef struct GHBN_Thread_Data {
  int ghbn_lock;
  char ghbn_hostname[MZ_MAX_HOSTNAME_LEN];
  char ghbn_servname[MZ_MAX_SERVNAME_LEN];
  struct mz_addrinfo ghbn_hints;
# ifdef USE_WINSOCK_TCP
  HANDLE ready_sema;
# else
  int ready_fd;
# endif
  struct mz_addrinfo *ghbn_result;
  int ghbn_err;
} GHBN_Thread_Data;

THREAD_LOCAL_DECL(GHBN_Thread_Data *ghbn_thread_data);

static intptr_t getaddrinfo_in_thread(void *_data)
  XFORM_SKIP_PROC
{
  GHBN_Thread_Data *data = (GHBN_Thread_Data *)_data;
  int ok;
  struct mz_addrinfo *res, hints;
  char hn_copy[MZ_MAX_HOSTNAME_LEN], sn_copy[MZ_MAX_SERVNAME_LEN];
# ifndef USE_WINSOCK_TCP
  int fd = data->ready_fd;
  int cr;
# endif
  
  if (data->ghbn_result) {
    mz_freeaddrinfo(data->ghbn_result);
    data->ghbn_result = NULL;
  }

  strcpy(hn_copy, data->ghbn_hostname);
  strcpy(sn_copy, data->ghbn_servname);
  memcpy(&hints, &data->ghbn_hints, sizeof(hints));

# ifdef USE_WINSOCK_TCP
  ReleaseSemaphore(data->ready_sema, 1, NULL);  
# else
  do {
    cr = write(fd, "?", 1);
  } while ((cr == -1) && (errno == EINTR));
# endif

  res = NULL;

  ok = mz_getaddrinfo(hn_copy[0] ? hn_copy : NULL, 
		      sn_copy[0] ? sn_copy : NULL, 
		      &hints, &res);

  data->ghbn_result = res;
  data->ghbn_err = ok;

# ifndef USE_WINSOCK_TCP
  {
    long v = 1;
    do {
      cr = write(fd, &v, sizeof(v));
    } while ((cr == -1) && (errno == EINTR));
    do {
      cr = close(fd);
    } while ((cr == -1) && (errno == EINTR));
  }
# endif

  return 1;
}

static void release_ghbn_lock(GHBN_Rec *rec)
{
  ghbn_thread_data->ghbn_lock = 0;
# ifdef USE_WINSOCK_TCP
  CloseHandle(rec->th);
# else
  close(rec->pin);
# endif
}

static int ghbn_lock_avail(Scheme_Object *_ignored)
{
  return !ghbn_thread_data->ghbn_lock;
}

static int ghbn_thread_done(Scheme_Object *_rec)
{
  GHBN_Rec *rec = (GHBN_Rec *)_rec;

  if (rec->done)
    return 1;

# ifdef USE_WINSOCK_TCP
  if (WaitForSingleObject(rec->th, 0) == WAIT_OBJECT_0) {
    rec->result = ghbn_thread_data->ghbn_result;
    ghbn_thread_data->ghbn_result = NULL;
    rec->err = ghbn_thread_data->ghbn_err;
    rec->done = 1;
    return 1;
  }
# else
  {
    long v;
    int cr;
    do {
      cr = read(rec->pin, &v, sizeof(long));
    } while ((cr == -1) && (errno == EINTR));
    if (cr > 0) {
      rec->result = ghbn_thread_data->ghbn_result;
      ghbn_thread_data->ghbn_result = NULL;
      rec->err = ghbn_thread_data->ghbn_err;
      rec->done = 1;
      return 1;
    }
  }
# endif

  return 0;
}

static void ghbn_thread_need_wakeup(Scheme_Object *_rec, void *fds)
{
  GHBN_Rec *rec = (GHBN_Rec *)_rec;

# ifdef USE_WINSOCK_TCP
  scheme_add_fd_handle((void *)rec->th, fds, 0);
# else
  {
    void *fds2;
    
    fds2 = MZ_GET_FDSET(fds, 2);
    
    MZ_FD_SET(rec->pin, (fd_set *)fds);
    MZ_FD_SET(rec->pin, (fd_set *)fds2);
  }
# endif
}

static int MZ_GETADDRINFO(const char *name, const char *svc, struct mz_addrinfo *hints, struct mz_addrinfo **res)
{
  GHBN_Rec *rec;
  int ok;

  if ((name && ((strlen(name) >= MZ_MAX_HOSTNAME_LEN) || !name[0]))
      || (svc && ((strlen(svc) >= MZ_MAX_SERVNAME_LEN) || !svc[0]))) {
    /* Give up on a separate thread. */
    return mz_getaddrinfo(name, svc, hints, res);
  }

  if (!ghbn_thread_data) {
    ghbn_thread_data = (GHBN_Thread_Data *)malloc(sizeof(GHBN_Thread_Data));
    memset(ghbn_thread_data, 0, sizeof(GHBN_Thread_Data));
  }

  rec = MALLOC_ONE_ATOMIC(GHBN_Rec);
  rec->done = 0;

  scheme_block_until(ghbn_lock_avail, NULL, NULL, 0);

  ghbn_thread_data->ghbn_lock = 1;

  if (name)
    strcpy(ghbn_thread_data->ghbn_hostname, name);
  else
    ghbn_thread_data->ghbn_hostname[0] = 0;
  if (svc)
    strcpy(ghbn_thread_data->ghbn_servname, svc);
  else
    ghbn_thread_data->ghbn_servname[0] = 0;
  memcpy(&ghbn_thread_data->ghbn_hints, hints, sizeof(*hints));

# ifdef USE_WINSOCK_TCP
  {
    HANDLE ready_sema;
    DWORD id;
    intptr_t th;
    
    ready_sema = CreateSemaphore(NULL, 0, 1, NULL);
    ghbn_thread_data->ready_sema = ready_sema;
    th = _beginthreadex(NULL, 5000, 
			(MZ_LPTHREAD_START_ROUTINE)getaddrinfo_in_thread,
			ghbn_thread_data, 0, &id);
    WaitForSingleObject(ghbn_thread_data->ready_sema, INFINITE);
    CloseHandle(ghbn_thread_data->ready_sema);
    
    rec->th = (HANDLE)th;
    ok = 1;
  }
# else
  {
    int p[2];
    if (pipe(p)) {
      ok = 0;
    } else {
      pthread_t t;
      rec->pin = p[0];
      ghbn_thread_data->ready_fd = p[1];
      if (pthread_create(&t, NULL, 
			 (MZ_LPTHREAD_START_ROUTINE)getaddrinfo_in_thread,
			 ghbn_thread_data)) {
	close(p[0]);
	close(p[1]);
	ok = 0;
      } else {
	char buf[1];
        int cr;
	pthread_detach(t);
        do {
          cr = read(rec->pin, buf, 1);
        } while ((cr == -1) && (errno == EINTR));
	fcntl(rec->pin, F_SETFL, MZ_NONBLOCKING);
	ok = 1;
      }
    }

    if (!ok) {
      getaddrinfo_in_thread(ghbn_thread_data);
      rec->result = ghbn_thread_data->ghbn_result;
      ghbn_thread_data->ghbn_result = NULL;
      rec->err = ghbn_thread_data->ghbn_err;
    }
  }
# endif

  if (ok) {
    BEGIN_ESCAPEABLE(release_ghbn_lock, rec);
    scheme_block_until(ghbn_thread_done, ghbn_thread_need_wakeup, (Scheme_Object *)rec, 0);
    END_ESCAPEABLE();

# ifdef USE_WINSOCK_TCP
    CloseHandle(rec->th);
# else
    close(rec->pin);
# endif
  }

  ghbn_thread_data->ghbn_lock = 0;

  *res = rec->result;

  return rec->err;
}

void scheme_free_ghbn_data() {
  if (ghbn_thread_data) {
    free(ghbn_thread_data);
    ghbn_thread_data = NULL;
  }
}
#else
# define MZ_GETADDRINFO mz_getaddrinfo
void scheme_free_ghbn_data() { }
#endif

#ifdef USE_SOCKETS_TCP

struct mz_addrinfo *scheme_get_host_address(const char *address, int id, int *err, 
					    int family, int passive, int tcp)
{
  char buf[32], *service;
  int ok;
  GC_CAN_IGNORE struct mz_addrinfo *r, hints;
  r = NULL;

  if (id >= 0) {
    service = buf;
    sprintf(buf, "%d", id);
  } else
    service = NULL;
  
  if (!address && !service) {
    *err = -1;
    return NULL;
  }

  memset(&hints, 0, sizeof(struct mz_addrinfo));
  hints.ai_family = ((family < 0) ? PF_UNSPEC : family);
  if (passive) {
    hints.ai_flags |= mzAI_PASSIVE;
  }
  if (tcp) {
    hints.ai_socktype = SOCK_STREAM;
# ifndef PROTOENT_IS_INT
    if (!proto) {
      proto = getprotobyname("tcp");
    }
# endif
    hints.ai_protocol= PROTO_P_PROTO;
  } else {
    hints.ai_socktype = SOCK_DGRAM;
  }

  ok = MZ_GETADDRINFO(address, service, &hints, &r);
  *err = ok;
  
  if (!ok)
    return r;
  else
    return NULL;
}

void scheme_free_host_address(struct mz_addrinfo *a)
{
  mz_freeaddrinfo(a);
}

const char *scheme_host_address_strerror(int errnum)
{
  return mz_gai_strerror(errnum);
}
#endif

/******************************* WinSock ***********************************/

#ifdef USE_WINSOCK_TCP

static int wsr_size = 0;
static tcp_t *wsr_array;

static void winsock_remember(tcp_t s)
{
  int i, new_size;
  tcp_t *naya;

# ifdef MZ_USE_PLACES
  WaitForSingleObject(winsock_sema, INFINITE);
# endif

  for (i = 0; i < wsr_size; i++) {
    if (!wsr_array[i]) {
      wsr_array[i] = s;
      break;
    }
  }

  if (i >= wsr_size) {
    if (!wsr_size) {
      new_size = 32;
    } else
      new_size = 2 * wsr_size;

    naya = malloc(sizeof(tcp_t) * new_size);
    for (i = 0; i < wsr_size; i++) {
      naya[i] = wsr_array[i];
    }

    naya[wsr_size] = s;

    if (wsr_array) free(wsr_array);

    wsr_array = naya;
    wsr_size = new_size;
  }  

# ifdef MZ_USE_PLACES
  ReleaseSemaphore(winsock_sema, 1, NULL);
# endif
}

static void winsock_forget(tcp_t s)
{
  int i;

# ifdef MZ_USE_PLACES
  WaitForSingleObject(winsock_sema, INFINITE);
# endif

  for (i = 0; i < wsr_size; i++) {
    if (wsr_array[i] == s) {
      wsr_array[i] = (tcp_t)NULL;
      break;
    }
  }

# ifdef MZ_USE_PLACES
  ReleaseSemaphore(winsock_sema, 1, NULL);
# endif
}

static int winsock_done(void)
{
  int i;

  /* only called in the original place */

  for (i = 0; i < wsr_size; i++) {
    if (wsr_array[i]) {
      closesocket(wsr_array[i]);
      wsr_array[i] = (tcp_t)NULL;
    }
  }

  return WSACleanup();
}

static void TCP_INIT(char *name)
{
  static int started = 0;
  
# ifdef MZ_USE_PLACES
  WaitForSingleObject(winsock_sema, INFINITE);
# endif

  if (!started) {
    WSADATA data;
    if (!WSAStartup(MAKEWORD(1, 1), &data)) {
      started = 1;
#ifdef __BORLANDC__
      atexit((void(*)())winsock_done);
#else      
      _onexit(winsock_done);
#endif
    }
  }

  if (!started)
    scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED,
		     "%s: no winsock driver",
		     name);
  
# ifdef MZ_USE_PLACES
  ReleaseSemaphore(winsock_sema, 1, NULL);
# endif
}
#else
/* Not Winsock */
# define TCP_INIT(x) /* nothing */
#endif

/*========================================================================*/
/*                       TCP ports and listeners                          */
/*========================================================================*/

#ifdef USE_SOCKETS_TCP
#define LISTENER_WAS_CLOSED(x) (((listener_t *)(x))->s[0] == INVALID_SOCKET)
#endif
#ifndef LISTENER_WAS_CLOSED
#define LISTENER_WAS_CLOSED(x) 0
#endif

/* Forward declaration */
static int stop_listener(Scheme_Object *o);

static Scheme_Object *listener_to_evt(listener_t *listener)
{
  Scheme_Object **a, *sema;
  int i;

  a = MALLOC_N(Scheme_Object*, listener->count);
  for (i = listener->count; i--; ) {
    sema = scheme_fd_to_semaphore(listener->s[i], MZFD_CREATE_READ, 1);
    if (!sema) 
      return NULL;
    a[i] = sema;
  }

  return scheme_make_evt_set(listener->count, a);
}

static int tcp_check_accept(Scheme_Object *_listener, Scheme_Schedule_Info *sinfo)
{
#ifdef USE_SOCKETS_TCP
  listener_t *listener = (listener_t *)_listener;
  int sr, i;
# ifndef HAVE_POLL_SYSCALL
  tcp_t s, mx;
  DECL_OS_FDSET(readfds);
  DECL_OS_FDSET(exnfds);
  struct timeval time = {0, 0};
# endif

  if (!sinfo || !sinfo->is_poll) {
    for (i = listener->count; i--; ) {
      if (check_fd_sema(listener->s[i], MZFD_CHECK_READ, NULL, NULL))
        break;
    }
    if (i < 0) return 0;
  }

# ifdef HAVE_POLL_SYSCALL
  if (LISTENER_WAS_CLOSED(listener))
    return 1;

  do {
    sr = poll(listener->pfd, listener->count, 0);
  } while ((sr == -1) && (errno == EINTR));

  if (sr) {
    for (i = listener->count; i--; ) {
      if (listener->pfd[i].revents)
        return i + 1;
    }
  }

  if (sr)
    return sr;
# else

  INIT_DECL_OS_RD_FDSET(readfds);
  INIT_DECL_OS_ER_FDSET(exnfds);

  if (LISTENER_WAS_CLOSED(listener))
    return 1;

  MZ_OS_FD_ZERO(readfds);
  MZ_OS_FD_ZERO(exnfds);

  mx = 0;
  for (i = 0; i < listener->count; i++) {
    s = listener->s[i];
    MZ_OS_FD_SET(s, readfds);
    MZ_OS_FD_SET(s, exnfds);
    if (s > mx)
      mx = s;
  }
  
  do {
    sr = select(mx + 1, readfds, NULL, exnfds, &time);
  } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));

  if (sr) {
    for (i = 0; i < listener->count; i++) {
      s = listener->s[i];
      if (MZ_OS_FD_ISSET(s, readfds)
	  || MZ_OS_FD_ISSET(s, exnfds))
	return i + 1;
    }
  }

  if (sr)
    return sr;
# endif

  if (sinfo && !sinfo->no_redirect) {
    Scheme_Object *evt;
    evt = listener_to_evt(listener);
    if (evt)
      scheme_set_sync_target(sinfo, evt, _listener, NULL, 0, 1, NULL);
  } else {
    for (i = listener->count; i--; ) {
      check_fd_sema(listener->s[i], MZFD_CREATE_READ, NULL, NULL);
    }
  }

#endif

  return 0;
}

static void tcp_accept_needs_wakeup(Scheme_Object *_listener, void *fds)
{
#ifdef USE_SOCKETS_TCP
  if (!LISTENER_WAS_CLOSED(_listener)) {
    listener_t *listener = (listener_t *)_listener;
    int i;
    tcp_t s;
    void *fds2;

    fds2 = MZ_GET_FDSET(fds, 2);
    
    for (i = 0; i < listener->count; i++) {
      s = listener->s[i];
      MZ_FD_SET(s, (fd_set *)fds);
      MZ_FD_SET(s, (fd_set *)fds2);
    }
  }
#endif
}

static int tcp_check_connect(Scheme_Object *connector_p, Scheme_Schedule_Info *sinfo)
{
#ifdef USE_SOCKETS_TCP
  tcp_t s;
  int sr;

  s = *(tcp_t *)connector_p;

  if (!sinfo || !sinfo->is_poll) {
    if (!check_fd_sema(s, MZFD_CHECK_WRITE, sinfo, NULL))
      return 0;
  }

# ifdef HAVE_POLL_SYSCALL
  {
    GC_CAN_IGNORE struct pollfd pfd[1];
    pfd[0].fd = s;
    pfd[0].events = POLLOUT;
    do {
      sr = poll(pfd, 1, 0);
    } while ((sr == -1) && (errno == EINTR));

    if (!sr) {
      /* fall through */
    } else if (pfd[0].revents & POLLOUT)
      return 1;
    else
      return -1;
  }
# else
  {
    DECL_OS_FDSET(writefds);
    DECL_OS_FDSET(exnfds);
    struct timeval time = {0, 0};
    
    INIT_DECL_OS_WR_FDSET(writefds);
    INIT_DECL_OS_ER_FDSET(exnfds);

    MZ_OS_FD_ZERO(writefds);
    MZ_OS_FD_ZERO(exnfds);
    
    MZ_OS_FD_SET(s, writefds);
    MZ_OS_FD_SET(s, exnfds);
    
    do {
      sr = select(s + 1, NULL, writefds, exnfds, &time);
    } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));
    
    if (!sr) {
      /* fall through */
    } else if (FD_ISSET(s, exnfds))
      return -1;
    else
      return 1;
  }
# endif

  check_fd_sema(s, MZFD_CREATE_WRITE, sinfo, NULL);

#endif
  return 0;
}

static void tcp_connect_needs_wakeup(Scheme_Object *connector_p, void *fds)
{
#ifdef USE_SOCKETS_TCP
  void *fds1, *fds2;
  tcp_t s = *(tcp_t *)connector_p;
  
  fds1 = MZ_GET_FDSET(fds, 1);
  fds2 = MZ_GET_FDSET(fds, 2);

  MZ_FD_SET(s, (fd_set *)fds1);
  MZ_FD_SET(s, (fd_set *)fds2);
#endif
}

static int tcp_check_write(Scheme_Object *port, Scheme_Schedule_Info *sinfo)
{
  Scheme_Tcp *data = (Scheme_Tcp *)((Scheme_Output_Port *)port)->port_data;
    
  if (((Scheme_Output_Port *)port)->closed)
    return 1;

  if (!sinfo || !sinfo->is_poll) {
    if (!check_fd_sema(data->tcp, MZFD_CHECK_WRITE, sinfo, port))
      return 0;
  }

#ifdef USE_SOCKETS_TCP
# ifdef HAVE_POLL_SYSCALL
  {
    GC_CAN_IGNORE struct pollfd pfd[1];
    int sr;

    pfd[0].fd = data->tcp;
    pfd[0].events = POLLOUT;
    do {
      sr = poll(pfd, 1, 0);
    } while ((sr == -1) && (errno == EINTR));

    if (!sr) {
      /* fall through */
    } else if (pfd[0].revents & POLLOUT)
      return 1;
    else
      return -1;
  }
# else
  {
    tcp_t s;
    DECL_OS_FDSET(writefds);
    DECL_OS_FDSET(exnfds);
    struct timeval time = {0, 0};
    int sr;
    
    INIT_DECL_OS_WR_FDSET(writefds);
    INIT_DECL_OS_ER_FDSET(exnfds);
    
    s = data->tcp;
    
    MZ_OS_FD_ZERO(writefds);
    MZ_OS_FD_SET(s, writefds);
    MZ_OS_FD_ZERO(exnfds);
    MZ_OS_FD_SET(s, exnfds);
    
    do {
      sr = select(s + 1, NULL, writefds, exnfds, &time);
    } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));
    
    if (sr)
      return sr;
  }
# endif
#else
  {
    TCPiopbX *xpb;
    TCPiopb *pb;
    int bytes;
    
    xpb = mac_make_xpb(data);
    pb = (TCPiopb *)xpb;
    
    pb->csCode = TCPStatus;
    if (mzPBControlSync((ParamBlockRec*)pb))
      bytes = -1;
    else {
      bytes = pb->csParam.status.sendWindow - pb->csParam.status.amtUnackedData;
      if (bytes < 0)
	bytes = 0;
    }
    
    return !!bytes;
  }
#endif

  check_fd_sema(data->tcp, MZFD_CREATE_WRITE, sinfo, port);

  return 0;
}

static void tcp_write_needs_wakeup(Scheme_Object *port, void *fds)
{
#ifdef USE_SOCKETS_TCP
  Scheme_Object *conn = ((Scheme_Output_Port *)port)->port_data;
  void *fds1, *fds2;
  tcp_t s = ((Scheme_Tcp *)conn)->tcp;
  
  fds1 = MZ_GET_FDSET(fds, 1);
  fds2 = MZ_GET_FDSET(fds, 2);
  
  MZ_FD_SET(s, (fd_set *)fds1);
  MZ_FD_SET(s, (fd_set *)fds2);
#endif
}


static Scheme_Tcp *make_tcp_port_data(MAKE_TCP_ARG int refcount)
{
  Scheme_Tcp *data;
  char *bfr;
  
  data = MALLOC_ONE_RT(Scheme_Tcp);
#ifdef MZTAG_REQUIRED
  data->b.type = scheme_rt_tcp;
#endif
#ifdef USE_SOCKETS_TCP
  data->tcp = tcp;
#endif

  bfr = (char *)scheme_malloc_atomic(TCP_BUFFER_SIZE);
  data->b.buffer = bfr;
  bfr = (char *)scheme_malloc_atomic(TCP_BUFFER_SIZE);
  data->b.out_buffer = bfr;

  data->b.bufpos = 0;
  data->b.bufmax = 0;
  data->b.hiteof = 0;
  data->b.refcount = refcount;

#ifdef USE_WINSOCK_TCP
  {
    unsigned long ioarg = 1;
    ioctlsocket(tcp, FIONBIO, &ioarg);
  }
#else
  fcntl(tcp, F_SETFL, MZ_NONBLOCKING);
#endif

  return data;
}

static int tcp_byte_ready (Scheme_Input_Port *port, Scheme_Schedule_Info *sinfo)
{
  Scheme_Tcp *data;
#ifdef USE_SOCKETS_TCP
  int sr;
# ifndef HAVE_POLL_SYSCALL
  DECL_OS_FDSET(readfds);
  DECL_OS_FDSET(exfds);
  struct timeval time = {0, 0};

  INIT_DECL_OS_RD_FDSET(readfds);
  INIT_DECL_OS_ER_FDSET(exfds);
# endif
#endif

  if (port->closed)
    return 1;

  data = (Scheme_Tcp *)port->port_data;

  if (data->b.hiteof)
    return 1;
  if (data->b.bufpos < data->b.bufmax)
    return 1;

  if (!sinfo || !sinfo->is_poll) {
    if (!check_fd_sema(data->tcp, MZFD_CHECK_READ, sinfo, (Scheme_Object *)port))
      return 0;
  }

#ifdef USE_SOCKETS_TCP
# ifdef HAVE_POLL_SYSCALL
  {
    GC_CAN_IGNORE struct pollfd pfd[1];

    pfd[0].fd = data->tcp;
    pfd[0].events = POLLIN;
    do {
      sr = poll(pfd, 1, 0);
    } while ((sr == -1) && (errno == EINTR));

    if (sr)
      return sr;
  }
# else
  {
    MZ_OS_FD_ZERO(readfds);
    MZ_OS_FD_ZERO(exfds);
    MZ_OS_FD_SET(data->tcp, readfds);
    MZ_OS_FD_SET(data->tcp, exfds);
    
    do {
      sr = select(data->tcp + 1, readfds, NULL, exfds, &time);
    } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));

    if (sr)
      return sr;
  }
# endif
#endif

  check_fd_sema(data->tcp, MZFD_CREATE_READ, sinfo, (Scheme_Object *)port);

  return 0;
}

static intptr_t tcp_get_string(Scheme_Input_Port *port, 
			   char *buffer, intptr_t offset, intptr_t size,
			   int nonblock,
			   Scheme_Object *unless)
{
  int errid;
  int read_amt;
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)port->port_data;

 top:

  if (scheme_unless_ready(unless))
    return SCHEME_UNLESS_READY;

  if (data->b.hiteof)
    return EOF;

  if (data->b.bufpos < data->b.bufmax) {
    int n;
    n = data->b.bufmax - data->b.bufpos;
    n = ((size <= n)
	 ? size
	 : n);
    
    memcpy(buffer + offset, data->b.buffer + data->b.bufpos, n);
    data->b.bufpos += n;
    
    return n;
  }
  
  while (!tcp_byte_ready(port, NULL)) {
    if (nonblock > 0)
      return 0;

#ifdef USE_SOCKETS_TCP
    {
      Scheme_Object *sema;
      sema = scheme_fd_to_semaphore(data->tcp, MZFD_CREATE_READ, 1);
      if (sema)
        scheme_wait_sema(sema, nonblock ? -1 : 0);
      else
        scheme_block_until_unless((Scheme_Ready_Fun)tcp_byte_ready,
                                  scheme_need_wakeup,
                                  (Scheme_Object *)port,
                                  0.0, unless,
                                  nonblock);
    }
#else
    do {
      scheme_thread_block_enable_break((float)0.0, nonblock);
      if (scheme_unless_ready(unless))
	break;
    } while (!tcp_byte_ready(port));
    scheme_current_thread->ran_some = 1;
#endif

    scheme_wait_input_allowed(port, nonblock);

    if (scheme_unless_ready(unless))
      return SCHEME_UNLESS_READY;
  }

  if (port->closed) {
    /* Another thread closed the input port while we were waiting. */
    /* Call scheme_get_byte to signal the error */
    scheme_get_byte((Scheme_Object *)port);
  }

  /* We assume that no other process has access to our sockets, so
     when we unblock, there's definitely something to read. */

  if (!data->b.bufmode || (size > TCP_BUFFER_SIZE))
    read_amt = TCP_BUFFER_SIZE;
  else
    read_amt = size;

#ifdef USE_SOCKETS_TCP
  {
    int rn;
    do {
      rn = recv(data->tcp, data->b.buffer, read_amt, 0);
    } while ((rn == -1) && (NOT_WINSOCK(errno) == EINTR));
    data->b.bufmax = rn;
  }
  errid = SOCK_ERRNO();

  /* Is it possible that an EAGAIN error occurs? That means that data
     isn't ready, even though select() says that data is ready. It
     seems to happen for at least one user, and there appears to be
     no harm in protecting against it. */
  if ((data->b.bufmax == -1) && WAS_EAGAIN(errid))
    goto top;

#endif
  
  if (data->b.bufmax == -1) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "tcp-read: error reading\n"
                     "  system error: %e",
		     errid);
    return 0;
  } else if (!data->b.bufmax) {
    data->b.hiteof = 1;
    return EOF;
  }

  {
    int n;
    n = data->b.bufmax;
    if (size < n)
      n = size;
    memcpy(buffer + offset, data->b.buffer, n);
    data->b.bufpos = n;

    return n;
  }
}

static void tcp_need_wakeup(Scheme_Input_Port *port, void *fds)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)port->port_data;

#ifdef USE_SOCKETS_TCP
  {
    void *fds2;
  
    fds2 = MZ_GET_FDSET(fds, 2);
    
    MZ_FD_SET(data->tcp, (fd_set *)fds);
    MZ_FD_SET(data->tcp, (fd_set *)fds2);
  }
#endif
}

static void tcp_close_input(Scheme_Input_Port *port)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)port->port_data;

#ifdef USE_SOCKETS_TCP
  if (!(data->flags & MZ_TCP_ABANDON_INPUT)) {
    int cr;
    do { 
      cr = shutdown(data->tcp, 0);
    } while ((cr == -1) && (errno == EINTR));
  }
#endif

  if (--data->b.refcount)
    return;

#ifdef USE_SOCKETS_TCP
  UNREGISTER_SOCKET(data->tcp);
  closesocket(data->tcp);
#endif

  (void)scheme_fd_to_semaphore(data->tcp, MZFD_REMOVE, 1);
}

static int
tcp_in_buffer_mode(Scheme_Port *p, int mode)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)((Scheme_Input_Port *)p)->port_data;  
  if (mode < 0)
    return data->b.bufmode;
  else {
    data->b.bufmode = mode;
    return mode;
  }
}

static intptr_t tcp_do_write_string(Scheme_Output_Port *port, 
				const char *s, intptr_t offset, intptr_t len, 
				int rarely_block, int enable_break)
{
  /* We've already checked for buffering before we got here. */
  /* If rarely_block is 1, it means only write as much as
     can be flushed immediately, blocking only if nothing
     can be written. */
  /* If rarely_block is 2, it means only write as much as
     can be flushed immediately, never ever blocking. */

  Scheme_Tcp *data;
  int errid, would_block = 0;
  intptr_t sent;

  data = (Scheme_Tcp *)port->port_data;

 top:

#ifdef USE_SOCKETS_TCP
  do {
    sent = send(data->tcp, s XFORM_OK_PLUS offset, len, 0);
  } while ((sent == -1) && (NOT_WINSOCK(errno) == EINTR));

  if (sent != len) {
#ifdef USE_WINSOCK_TCP
# define SEND_BAD_MSG_SIZE(e) (e == WSAEMSGSIZE)
#else    
# ifdef SEND_IS_NEVER_TOO_BIG
#  define SEND_BAD_MSG_SIZE(errid) 0
# else
#  define SEND_BAD_MSG_SIZE(errid) (errid == EMSGSIZE)
# endif
#endif
    errid = SOCK_ERRNO();
    if (sent > 0) {
      /* Some data was sent. Return, or recur to handle the rest. */
      if (rarely_block)
	return sent;
      else
	sent += tcp_do_write_string(port, s, offset + sent, len - sent, 0, enable_break);
      errid = 0;
    } else if ((len > 1) && SEND_BAD_MSG_SIZE(errid)) {
      /* split the message and try again: */
      int half = (len / 2);
      sent = tcp_do_write_string(port, s, offset, half, rarely_block, enable_break);
      if (rarely_block)
	return sent;
      sent += tcp_do_write_string(port, s, offset + half, len - half, 0, enable_break);
      errid = 0;
    } else if (WAS_EAGAIN(errid)) {
      errid = 0;
      would_block = 1;
    }
  } else
    errid = 0;
#endif

  if (would_block) {
    if (rarely_block == 2)
      return 0;

    /* Block for writing: */
    {
      Scheme_Object *sema;
      sema = scheme_fd_to_semaphore(data->tcp, MZFD_CREATE_WRITE, 1);
      if (sema)
        scheme_wait_sema(sema, enable_break ? -1 : 0);
      else
        scheme_block_until_enable_break((Scheme_Ready_Fun)tcp_check_write, 
                                        tcp_write_needs_wakeup, 
                                        (Scheme_Object *)port, 
                                        (float)0.0, enable_break);
    }

    /* Closed while blocking? */
    if (((Scheme_Output_Port *)port)->closed) {
      /* Call write again to signal the error: */
      scheme_put_byte_string("tcp-write-string", (Scheme_Object *)port, s, offset, len, 0);
      return sent + len; /* shouldn't get here */
    }

    /* Ok - try again! */
    would_block = 0;
    goto top;
  }

  if (errid)
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "tcp-write: error writing\n"
                     "  system error: %e",
		     errid);

  return sent;
}

static int tcp_flush(Scheme_Output_Port *port,
		     int rarely_block, int enable_break)
{
  Scheme_Tcp *data;
  int amt, flushed = 0;
  
  data = (Scheme_Tcp *)port->port_data;

  while (1) {
    if (data->b.out_bufpos == data->b.out_bufmax) {
      data->b.out_bufpos = 0;
      data->b.out_bufmax = 0;
      return flushed;
    }
    amt = tcp_do_write_string(port, data->b.out_buffer, data->b.out_bufpos, 
			      data->b.out_bufmax - data->b.out_bufpos,
			      rarely_block, enable_break);
    flushed += amt;
    data->b.out_bufpos += amt;
    if (rarely_block && (data->b.out_bufpos < data->b.out_bufmax))
      return flushed;
  }
}

static intptr_t tcp_write_string(Scheme_Output_Port *port, 
			     const char *s, intptr_t offset, intptr_t len, 
			     int rarely_block, int enable_break)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)port->port_data;

  if (!len) {
    /* Flush */
    tcp_flush(port, rarely_block, enable_break);
    if (data->b.out_bufpos != data->b.out_bufmax)
      return -1;
    return 0;
  }

  if (rarely_block) {
    tcp_flush(port, rarely_block, enable_break);
    if (data->b.out_bufmax)
      return -1;
  } else {
    if (data->b.out_bufmode < 2) {
      if (data->b.out_bufmax + len < TCP_BUFFER_SIZE) {
	memcpy(data->b.out_buffer + data->b.out_bufmax, s + offset, len);
	data->b.out_bufmax += (short)len;
	if (data->b.out_bufmode == 1) {
	  /* Check for newline */
	  int i;
	  for (i = 0; i < len; i++) {
	    if ((s[offset + i] == '\r')
		|| (s[offset + i] == '\n'))
	      break;
	  }
	  if (i < len)
	    tcp_flush(port, rarely_block, enable_break);
	}
	return len;
      }
    }
    tcp_flush(port, rarely_block, enable_break);
  }

  /* When we get here, the buffer is empty */
  return tcp_do_write_string(port, s, offset, len, rarely_block, enable_break);
}

static void tcp_close_output(Scheme_Output_Port *port)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)port->port_data;

  if (data->b.out_bufmax && !scheme_force_port_closed)
    tcp_flush(port, 0, 0);

#ifdef USE_SOCKETS_TCP
  if (!(data->flags & MZ_TCP_ABANDON_OUTPUT)) {
    int cr;
    do { 
      cr = shutdown(data->tcp, 1);
    } while ((cr == -1) && (errno == EINTR));
  }
#endif

  if (--data->b.refcount)
    return;

#ifdef USE_SOCKETS_TCP
  UNREGISTER_SOCKET(data->tcp);
  closesocket(data->tcp);
#endif

  (void)scheme_fd_to_semaphore(data->tcp, MZFD_REMOVE, 1);
}

static int
tcp_out_buffer_mode(Scheme_Port *p, int mode)
{
  Scheme_Tcp *data;

  data = (Scheme_Tcp *)((Scheme_Output_Port *)p)->port_data;  
  if (mode < 0)
    return data->b.out_bufmode;
  else {
    int go;
    go = (mode > data->b.out_bufmode);
    data->b.out_bufmode = mode;
    if (go)
      tcp_flush((Scheme_Output_Port *)p, 0, 0);
    return mode;
  }
}

static Scheme_Object *
make_tcp_input_port_symbol_name(void *data, Scheme_Object *name, Scheme_Object *cust)
{
  Scheme_Input_Port *ip;

  if (cust)
    scheme_set_next_port_custodian((Scheme_Custodian *)cust);
  
  ip = scheme_make_input_port(scheme_tcp_input_port_type,
			      data,
                              name,
			      tcp_get_string,
			      NULL,
			      scheme_progress_evt_via_get,
			      scheme_peeked_read_via_get,
			      (Scheme_In_Ready_Fun)tcp_byte_ready,
			      tcp_close_input,
			      tcp_need_wakeup,
			      1);

  ip->p.buffer_mode_fun = tcp_in_buffer_mode;

  return (Scheme_Object *)ip;
}

static Scheme_Object *
make_tcp_input_port(void *data, const char *name, Scheme_Object *cust)
{
  return make_tcp_input_port_symbol_name(data, scheme_intern_symbol(name), cust);
}

static Scheme_Object *
make_tcp_output_port_symbol_name(void *data, Scheme_Object *name, Scheme_Object *cust)
{
  Scheme_Output_Port *op;

  if (cust)
    scheme_set_next_port_custodian((Scheme_Custodian *)cust);

  op = scheme_make_output_port(scheme_tcp_output_port_type,
						  data,
						  name,
						  scheme_write_evt_via_write,
						  tcp_write_string,
						  (Scheme_Out_Ready_Fun)tcp_check_write,
						  tcp_close_output,
						  (Scheme_Need_Wakeup_Output_Fun)tcp_write_needs_wakeup,
						  NULL,
						  NULL,
						  1);

  op->p.buffer_mode_fun = tcp_out_buffer_mode;

  return (Scheme_Object *)op;
}

static Scheme_Object *
make_tcp_output_port(void *data, const char *name, Scheme_Object *cust)
{
  return make_tcp_output_port_symbol_name(data, scheme_intern_symbol(name), cust);
}

#endif /* USE_TCP */

/*========================================================================*/
/*                         TCP Racket interface                           */
/*========================================================================*/

#ifdef USE_SOCKETS_TCP
typedef struct Close_Socket_Data {
  tcp_t s;
  struct mz_addrinfo *src_addr, *dest_addr;
} Close_Socket_Data;

static void closesocket_w_decrement(Close_Socket_Data *csd)
{
  closesocket(csd->s);
  (void)scheme_fd_to_semaphore(csd->s, MZFD_REMOVE, 1);
  if (csd->src_addr)
    mz_freeaddrinfo(csd->src_addr);
  mz_freeaddrinfo(csd->dest_addr);  
}
#endif

const char *scheme_hostname_error(int err)
{
#ifdef USE_SOCKETS_TCP
  return mz_gai_strerror(err);
#else
  return "?";
#endif
}

static Scheme_Object *tcp_connect(int argc, Scheme_Object *argv[])
{
  char * volatile address = "", * volatile src_address, * volatile errmsg = NULL;
  unsigned short origid, id, src_origid, src_id;
  int errpart = 0, errid = 0;
  volatile int nameerr = 0, no_local_spec;
  Scheme_Object *bs, *src_bs;
#ifdef USE_SOCKETS_TCP
  GC_CAN_IGNORE struct mz_addrinfo *tcp_connect_dest;
  GC_CAN_IGNORE struct mz_addrinfo * volatile tcp_connect_src;
#endif

  if (!SCHEME_CHAR_STRINGP(argv[0]))
    scheme_wrong_contract("tcp-connect", "string?", 0, argc, argv);
  if (!CHECK_PORT_ID(argv[1]))
    scheme_wrong_contract("tcp-connect", PORT_ID_TYPE, 1, argc, argv);
  if (argc > 2)
    if (!SCHEME_CHAR_STRINGP(argv[2]) && !SCHEME_FALSEP(argv[2]))
      scheme_wrong_contract("tcp-connect", "(or/c string? #f)", 2, argc, argv);
  if (argc > 3)
    if (SCHEME_TRUEP(argv[3]) && !CHECK_PORT_ID(argv[3]))
      scheme_wrong_contract("tcp-connect", "(or/c " PORT_ID_TYPE " #f)", 3, argc, argv);

#ifdef USE_TCP
  TCP_INIT("tcp-connect");
#endif

  bs = argv[0];
  if (SCHEME_CHAR_STRINGP(bs))
    bs = scheme_char_string_to_byte_string(bs);

  address = SCHEME_BYTE_STR_VAL(bs);
  origid = (unsigned short)SCHEME_INT_VAL(argv[1]);

  if ((argc > 2) && SCHEME_TRUEP(argv[2])) {
    src_bs = scheme_char_string_to_byte_string(argv[2]);
    src_address = SCHEME_BYTE_STR_VAL(src_bs);
  } else
    src_address = NULL;
   
  if ((argc > 3) && SCHEME_TRUEP(argv[3])) {
    no_local_spec = 0;
    src_origid = (unsigned short)SCHEME_INT_VAL(argv[3]);
  } else {
    no_local_spec = 1;
    src_origid = 0;
    if (src_address) {
      scheme_contract_error("tcp-connect",
                            "no local port number supplied when local hostname was supplied",
                            "hostname", 1, argv[2],
                            NULL);
    }
  }

  scheme_security_check_network("tcp-connect", address, origid, 1);
  scheme_custodian_check_available(NULL, "tcp-connect", "network");

#ifdef USE_TCP
  id = origid;
  src_id = src_origid;
#endif

#ifdef USE_SOCKETS_TCP
  tcp_connect_dest = scheme_get_host_address(address, id, &errid, -1, 0, 1);
  if (tcp_connect_dest) {
    if (no_local_spec)
      tcp_connect_src = NULL;
    else
      tcp_connect_src = scheme_get_host_address(src_address, src_id, &errid, -1, 1, 1);
    if (no_local_spec || tcp_connect_src) {
      GC_CAN_IGNORE struct mz_addrinfo * volatile addr;
      for (addr = tcp_connect_dest; addr; addr = addr->ai_next) {
	tcp_t s;
	s = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
	if (s != INVALID_SOCKET) {
	  int status, inprogress;
	  if (no_local_spec
	      || !bind(s, tcp_connect_src->ai_addr, tcp_connect_src->ai_addrlen)) {
#ifdef USE_WINSOCK_TCP
	    unsigned long ioarg = 1;
	    ioctlsocket(s, FIONBIO, &ioarg);
#else
	    int size = TCP_SOCKSENDBUF_SIZE;
	    fcntl(s, F_SETFL, MZ_NONBLOCKING);
# ifndef CANT_SET_SOCKET_BUFSIZE
	    setsockopt(s, SOL_SOCKET, SO_SNDBUF, (char *)&size, sizeof(int));
# endif
#endif
	    status = connect(s, addr->ai_addr, addr->ai_addrlen);
#ifdef USE_UNIX_SOCKETS_TCP
	    if (status)
	      status = errno;
	    if (status == EINTR)
	      status = EINPROGRESS;
	
	    inprogress = (status == EINPROGRESS);
#endif
#ifdef USE_WINSOCK_TCP
	    if (status)
	      status = WSAGetLastError();

	    inprogress = (status == WSAEWOULDBLOCK);
	    errno = status;
#endif

	  
	    if (inprogress) {
	      tcp_t *sptr;
	      Close_Socket_Data *csd;
              Scheme_Object *sema;

	      sptr = (tcp_t *)scheme_malloc_atomic(sizeof(tcp_t));
	      *sptr = s;

	      csd = (Close_Socket_Data *)scheme_malloc_atomic(sizeof(Close_Socket_Data));
	      csd->s = s;
	      csd->src_addr = tcp_connect_src;
	      csd->dest_addr = tcp_connect_dest;

              sema = scheme_fd_to_semaphore(s, MZFD_CREATE_WRITE, 1);

	      BEGIN_ESCAPEABLE(closesocket_w_decrement, csd);
              if (sema)
                scheme_wait_sema(sema, 0);
              else
                scheme_block_until((Scheme_Ready_Fun)tcp_check_connect, 
                                   tcp_connect_needs_wakeup, 
                                   (void *)sptr, 
                                   (float)0.0);
	      END_ESCAPEABLE();

	      /* Check whether connect succeeded, or get error: */
	      {
		unsigned int so_len = sizeof(status);
		if (getsockopt(s, SOL_SOCKET, SO_ERROR, (void *)&status, &so_len) != 0) {
		  status = SOCK_ERRNO();
		}
		errno = status; /* for error reporting, below */
	      }

#ifdef USE_WINSOCK_TCP
	      if (scheme_stupid_windows_machine > 0) {
		/* getsockopt() seems not to work in Windows 95, so use the
		   result from select(), which seems to reliably detect an error condition */
		if (!status) {
		  if (tcp_check_connect((Scheme_Object *)sptr, NULL) == -1) {
		    status = 1;
		    errno = WSAECONNREFUSED; /* guess! */
		  }
		}
	      }
#endif
	    }
	
	    if (!status) {
	      Scheme_Object *v[2];
	      Scheme_Tcp *tcp;

	      if (tcp_connect_src)
		mz_freeaddrinfo(tcp_connect_src);
	      mz_freeaddrinfo(tcp_connect_dest);

	      tcp = make_tcp_port_data(s, 2);
	      
	      v[0] = make_tcp_input_port(tcp, address, NULL);
	      v[1] = make_tcp_output_port(tcp, address, NULL);
	      
	      REGISTER_SOCKET(s);

	      return scheme_values(2, v);
	    } else {
	      errid = errno;
	      closesocket(s);
              (void)scheme_fd_to_semaphore(s, MZFD_REMOVE, 1);
	      errpart = 6;
	    }
	  } else {
	    errpart = 5;
	    errid = SOCK_ERRNO();
	  }
	} else {
	  errpart = 4;
	  errid = SOCK_ERRNO();
	}
      }
      if (tcp_connect_src)
	mz_freeaddrinfo(tcp_connect_src);
    } else {
      errpart = 2;
      nameerr = 1;
      errmsg = "local host not found";
    } 
    if (tcp_connect_dest)
      mz_freeaddrinfo(tcp_connect_dest);
  } else {
    errpart = 1;
    nameerr = 1;
    errmsg = "host not found";
  }
#endif

#ifdef USE_TCP
  scheme_raise_exn(MZEXN_FAIL_NETWORK,
		   "tcp-connect: connection failed\n"
                   "%s%s%s"
                   "  address: %s\n"
                   "  port number: %d\n"
                   "  step: %d\n"
                   "  system error: %N",
                   errmsg ? "  detail: " : "",
                   errmsg ? errmsg : "",
                   errmsg ? "\n" : "",
		   address, origid, errpart, 
                   nameerr, errid);
#else
  scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED,
		   "tcp-connect: " NOT_SUPPORTED_STR);
#endif

  return NULL;
}

static Scheme_Object *
tcp_connect_break(int argc, Scheme_Object *argv[])
{
  return scheme_call_enable_break(tcp_connect, argc, argv);
}


static unsigned short get_no_portno(tcp_t socket, int *_errid)
{
  char here[MZ_SOCK_NAME_MAX_LEN];
  struct sockaddr_in *addr_in;
  unsigned int l = sizeof(here);
  unsigned short no_port;


  if (getsockname(socket, (struct sockaddr *)here, &l)) {
    int errid;
    errid = SOCK_ERRNO();
    *_errid = errid;
    return 0;
  }

  /* don't use ntohs, since the result is put back into another sin_port: */
  addr_in = (struct sockaddr_in *)here;
  no_port = addr_in->sin_port;
  if (!no_port)
    *_errid = 0;
  return no_port;
}

static Scheme_Object *
tcp_listen(int argc, Scheme_Object *argv[])
{
  unsigned short id, origid;
  int backlog, errid;
  int reuse = 0;
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
  int no_ipv6 = 0;
#endif
  const char *address;
  
  if (!CHECK_LISTEN_PORT_ID(argv[0]))
    scheme_wrong_contract("tcp-listen", LISTEN_PORT_ID_TYPE, 0, argc, argv);
  if (argc > 1) {
    if (!((SCHEME_INTP(argv[1]) && (SCHEME_INT_VAL(argv[1]) >= 1))
          || (SCHEME_BIGNUMP(argv[1]) && SCHEME_BIGPOS(argv[1]))))
      scheme_wrong_contract("tcp-listen", "exact-positive-integer?", 1, argc, argv);
  }
  if (argc > 2)
    reuse = SCHEME_TRUEP(argv[2]);
  if (argc > 3) {
    if (!SCHEME_CHAR_STRINGP(argv[3]) && !SCHEME_FALSEP(argv[3]))
      scheme_wrong_contract("tcp-listen", "(or/c string? #f)", 3, argc, argv);
  }
    
#ifdef USE_TCP
  TCP_INIT("tcp-listen");
#endif

  origid = (unsigned short)SCHEME_INT_VAL(argv[0]);
  if (argc > 1) {
    if (SCHEME_INTP(argv[1]))
      backlog = SCHEME_INT_VAL(argv[1]);
    else 
      backlog = 1024;
  } else
    backlog = 4;
  if ((argc > 3) && SCHEME_TRUEP(argv[3])) {
    Scheme_Object *bs;
    bs = scheme_char_string_to_byte_string(argv[3]);
    address = SCHEME_BYTE_STR_VAL(bs);
  } else
    address = NULL;

  scheme_security_check_network("tcp-listen", address, origid, 0);
  scheme_custodian_check_available(NULL, "tcp-listen", "network");

#ifdef USE_TCP
  id = origid;
#endif

#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
 retry:
#endif

  {
    GC_CAN_IGNORE struct mz_addrinfo *tcp_listen_addr, *addr;
    int err, count = 0, pos = 0, i;
    listener_t *l = NULL;
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
    int any_v4 = 0, any_v6 = 0;
#endif

    tcp_listen_addr = scheme_get_host_address(address, id, &err, 
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
					      no_ipv6 ? MZ_PF_INET : -1,
#else
					      -1, 
#endif
					      1, 1);

    for (addr = tcp_listen_addr; addr; addr = addr->ai_next) {
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
      if (addr->ai_family == MZ_PF_INET)
	any_v4 = 1;
      else if (addr->ai_family == PF_INET6)
	any_v6 = 1;
#endif
      count++;
    }
		
    if (tcp_listen_addr) {
      tcp_t s;
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
      /* Try IPv6 listeners first, so we can retry and use just IPv4 if
	 IPv6 doesn't work right. */
      int v6_loop = (any_v6 && any_v4), skip_v6 = 0;
#endif
      int first_time = 1;
      int first_was_zero = 0;
      unsigned short no_port = 0;

      errid = 0;
      for (addr = tcp_listen_addr; addr; ) {
#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
	if ((v6_loop && (addr->ai_family != PF_INET6))
	    || (skip_v6 && (addr->ai_family == PF_INET6))) {
	  addr = addr->ai_next;
	  if (v6_loop && !addr) {
	    v6_loop = 0;
	    skip_v6 = 1;
	    addr = tcp_listen_addr;
	  }
	  continue;
	}
#endif

	s = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);

#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
	if (s == INVALID_SOCKET) {
	  /* Maybe it failed because IPv6 is not available: */
	  if ((addr->ai_family == PF_INET6) && (errno == EAFNOSUPPORT)) {
	    if (any_v4 && !pos) {
	      /* Maybe we can make it work with just IPv4. Try again. */
	      no_ipv6 = 1;
	      mz_freeaddrinfo(tcp_listen_addr);
	      goto retry;
	    }
	  }
	}
	if (s != INVALID_SOCKET) {
	  if (any_v4 && (addr->ai_family == PF_INET6)) {
	    int ok;
# ifdef IPV6_V6ONLY
	    int on = 1;
	    ok = setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
# else
	    ok = -1;
# endif
	    if (ok) {
	      if (!pos) {
		/* IPV6_V6ONLY doesn't work */
		no_ipv6 = 1;
		mz_freeaddrinfo(tcp_listen_addr);
		goto retry;
	      } else {
		errid = errno;
		closesocket(s);
                (void)scheme_fd_to_semaphore(s, MZFD_REMOVE, 1);
		errno = errid;
		s = INVALID_SOCKET;
	      }
	    }
	  }
	}
#endif

	if (s != INVALID_SOCKET) {
#ifdef USE_WINSOCK_TCP
	  unsigned long ioarg = 1;
	  ioctlsocket(s, FIONBIO, &ioarg);
#else
	  fcntl(s, F_SETFL, MZ_NONBLOCKING);
#endif

	  if (reuse) {
	    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *)(&reuse), sizeof(int));
	  }
      
          if (first_was_zero) {
            ((struct sockaddr_in *)addr->ai_addr)->sin_port = no_port;
          }
	  if (!bind(s, addr->ai_addr, addr->ai_addrlen)) {
            if (first_time) {
              if (((struct sockaddr_in *)addr->ai_addr)->sin_port == 0) {
                no_port = get_no_portno(s, &errid);
                first_was_zero = 1;
		if (no_port == 0) {
		  closesocket(s);
		  break;
		}
              }
              first_time = 0;
            }

	    if (!listen(s, backlog)) {
	      if (!pos) {
		l = scheme_malloc_tagged(sizeof(listener_t) + ((count - mzFLEX_DELTA) * sizeof(tcp_t)));
		l->so.type = scheme_listener_type;
		l->count = count;
# ifdef HAVE_POLL_SYSCALL
                {
                  struct pollfd *pfd;
                  pfd = (struct pollfd *)scheme_malloc_atomic(sizeof(struct pollfd) * count);
                  l->pfd = pfd;
                }
# endif
		{
		  Scheme_Custodian_Reference *mref;
		  mref = scheme_add_managed(NULL,
					    (Scheme_Object *)l,
					    (Scheme_Close_Custodian_Client *)stop_listener,
					    NULL,
					    1);
		  l->mref = mref;
		}
	      }
# ifdef HAVE_POLL_SYSCALL
              l->pfd[pos].fd = s;
              l->pfd[pos].events = POLLIN;
# endif
	      l->s[pos++] = s;
	    
	      REGISTER_SOCKET(s);

	      if (pos == count) {
		mz_freeaddrinfo(tcp_listen_addr);

		return (Scheme_Object *)l;
	      }
	    } else {
	      errid = SOCK_ERRNO();
	      closesocket(s);
	      break;
	    }
	  } else {
	    errid = SOCK_ERRNO();
	    closesocket(s);
	    break;
	  }
	} else {
	  errid = SOCK_ERRNO();
	  break;
	}

	addr = addr->ai_next;

#ifdef MZ_TCP_LISTEN_IPV6_ONLY_SOCKOPT
	if (!addr && v6_loop) {
	  v6_loop = 0;
	  skip_v6 = 1;
	  addr = tcp_listen_addr;
	}
#endif
      }

      for (i = 0; i < pos; i++) {
	s = l->s[i];
	UNREGISTER_SOCKET(s);
	closesocket(s);
      }
      
      mz_freeaddrinfo(tcp_listen_addr);
    } else {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "tcp-listen: host lookup failed\n"
                       "  address: %s\n"
                       "  system error: %N",
		       address ? address : "#f", 1, err);
      return NULL;
    }
  }

#ifdef USE_TCP
  scheme_raise_exn(MZEXN_FAIL_NETWORK,
		   "tcp-listen: listen failed\n"
                   "  port number: %d\n"
                   "  system error: %E",
		   (int)origid, errid);
#else
  scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED,
		   "tcp-listen: " NOT_SUPPORTED_STR);
#endif

  return NULL;
}

#ifdef USE_TCP
static int stop_listener(Scheme_Object *o)
{
  int was_closed = 0;

#ifdef USE_SOCKETS_TCP
  {
    listener_t *listener = (listener_t *)o;
    int i;
    tcp_t s;
    s = listener->s[0];
    if (s == INVALID_SOCKET)
      was_closed = 1;
    else {
      for (i = 0; i < listener->count; i++) {
	s = listener->s[i];
	UNREGISTER_SOCKET(s);
	closesocket(s);
        (void)scheme_fd_to_semaphore(s, MZFD_REMOVE, 1);
	listener->s[i] = INVALID_SOCKET;
      }
      scheme_remove_managed(((listener_t *)o)->mref, o);
    }
  }
#endif

  return was_closed;
}
#endif

static Scheme_Object *
tcp_stop(int argc, Scheme_Object *argv[])
{
#ifdef USE_TCP
  int was_closed;

  if (!SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_listener_type))
    scheme_wrong_contract("tcp-close", "tcp-listener?", 0, argc, argv);

  TCP_INIT("tcp-close");

  was_closed = stop_listener(argv[0]);

  if (was_closed) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "tcp-close: listener was already closed");
    return NULL;
  }

  return scheme_void;
#else
  scheme_wrong_contract("tcp-close", "tcp-listener?", 0, argc, argv);
  return NULL;
#endif
}

static Scheme_Object *
tcp_accept_ready(int argc, Scheme_Object *argv[])
{
#ifdef USE_TCP
  int ready;

  if (!SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_listener_type))
    scheme_wrong_contract("tcp-accept-ready?", "tcp-listener?", 0, argc, argv);

  TCP_INIT("tcp-accept-ready?");

  if (LISTENER_WAS_CLOSED(argv[0])) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "tcp-accept-ready?: listener is closed");
    return NULL;
  }

  ready = tcp_check_accept(argv[0], NULL);

  return (ready ? scheme_true : scheme_false);
#else
  scheme_wrong_contract("tcp-accept-ready?", "tcp-listener?", 0, argc, argv);
  return NULL;
#endif
}

static Scheme_Object *
do_tcp_accept(int argc, Scheme_Object *argv[], Scheme_Object *cust, char **_fail_reason)
/* If _fail_reason is not NULL, never raise an exception. */
{
#ifdef USE_TCP
  int was_closed = 0, errid, ready_pos;
  Scheme_Object *listener;
# ifdef USE_SOCKETS_TCP
  tcp_t s, ls;
  unsigned int l;
  GC_CAN_IGNORE char tcp_accept_addr[MZ_SOCK_NAME_MAX_LEN];
# endif

  if (!SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_listener_type))
    scheme_wrong_contract("tcp-accept", "tcp-listener?", 0, argc, argv);

  TCP_INIT("tcp-accept");

  listener = argv[0];

  was_closed = LISTENER_WAS_CLOSED(listener);

  if (!was_closed) {
    ready_pos = tcp_check_accept(listener, NULL);
    if (!ready_pos) {
      Scheme_Object *evt;
      evt = listener_to_evt((listener_t *)listener);
      if (evt)
        scheme_sync(1, &evt);
      else
        scheme_block_until((Scheme_Ready_Fun)tcp_check_accept, 
                           tcp_accept_needs_wakeup, 
                           listener, 
                           0.0);
      ready_pos = tcp_check_accept(listener, NULL);
    }
    was_closed = LISTENER_WAS_CLOSED(listener);
  } else
    ready_pos = 0;

  if (was_closed) {
    if (_fail_reason)
      *_fail_reason = "tcp-accept-evt: listener is closed";
    else
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
                       "tcp-accept: listener is closed");
    return NULL;
  }

  if (!_fail_reason)
    scheme_custodian_check_available((Scheme_Custodian *)cust, "tcp-accept", "network");
  else {
    if (!scheme_custodian_is_available((Scheme_Custodian *)cust)) {
      *_fail_reason = "tcp-accept-evt: custodian is shutdown";
      return NULL;
    }
  }
  
# ifdef USE_SOCKETS_TCP
  ls = ((listener_t *)listener)->s[ready_pos-1];

  l = sizeof(tcp_accept_addr);

  do {
    s = accept(ls, (struct sockaddr *)tcp_accept_addr, &l);
  } while ((s == -1) && (NOT_WINSOCK(errno) == EINTR));

  if (s != INVALID_SOCKET) {
    Scheme_Object *v[2];
    Scheme_Tcp *tcp;
    
#  ifdef USE_UNIX_SOCKETS_TCP
    int size = TCP_SOCKSENDBUF_SIZE;
#   ifndef CANT_SET_SOCKET_BUFSIZE
    setsockopt(s, SOL_SOCKET, SO_SNDBUF, (char *)&size, sizeof(int));
#   endif
#  endif

    tcp = make_tcp_port_data(s, 2);

    v[0] = make_tcp_input_port(tcp, "tcp-accepted", cust);
    v[1] = make_tcp_output_port(tcp, "tcp-accepted", cust);

    REGISTER_SOCKET(s);
    
    return scheme_values(2, v);
  }
  errid = SOCK_ERRNO();
# endif
  
  if (_fail_reason)
    *_fail_reason = "tcp-accept-evt: accept from listener failed";
  else
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
                     "tcp-accept: accept from listener failed\n"
                     "  system error: %E", 
                     errid);
#else
  scheme_wrong_contract("tcp-accept", "tcp-listener?", 0, argc, argv);
#endif

  return NULL;
}

static Scheme_Object *
tcp_accept(int argc, Scheme_Object *argv[])
{
  return do_tcp_accept(argc, argv, NULL, NULL);
}

static Scheme_Object *
tcp_accept_break(int argc, Scheme_Object *argv[])
{
  return scheme_call_enable_break(tcp_accept, argc, argv);
}

void register_network_evts()
{
#ifdef USE_TCP
  scheme_add_evt(scheme_listener_type, (Scheme_Ready_Fun)tcp_check_accept, tcp_accept_needs_wakeup, NULL, 0);
  scheme_add_evt(scheme_tcp_accept_evt_type, (Scheme_Ready_Fun)tcp_check_accept_evt, tcp_accept_evt_needs_wakeup, NULL, 0);
# ifdef UDP_IS_SUPPORTED
  scheme_add_evt(scheme_udp_evt_type, (Scheme_Ready_Fun)udp_evt_check_ready, udp_evt_needs_wakeup, NULL, 0);
# endif
#endif
}

static Scheme_Object *tcp_listener_p(int argc, Scheme_Object *argv[])
{
   return (SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_listener_type)
	   ? scheme_true
	   : scheme_false);
}

void scheme_getnameinfo(void *sa, int salen, 
			char *host, int hostlen,
			char *serv, int servlen)
{
#ifdef HAVE_GETADDRINFO
  getnameinfo(sa, salen, host, hostlen, serv, servlen,
	      NI_NUMERICHOST | NI_NUMERICSERV);
#else
  if (host) {
    unsigned char *b;
    b = (unsigned char *)&((struct sockaddr_in *)sa)->sin_addr;
    sprintf(host, "%d.%d.%d.%d", b[0], b[1], b[2], b[3]);
  }
  if (serv) {
    int id;
    id = ntohs(((struct sockaddr_in *)sa)->sin_port);
    sprintf(serv, "%d", id);
  }
#endif
}

static int extract_svc_value(char *svc_buf)
{
  int id = 0, j;
  for (j = 0; svc_buf[j]; j++) {
    id = (id * 10) + (svc_buf[j] - '0');
  }
  return id;
}

#define SCHEME_LISTEN_PORTP(p) SAME_TYPE(SCHEME_TYPE(p), scheme_listener_type)
#define SCHEME_UDP_PORTP(p) SAME_TYPE(SCHEME_TYPE(p), scheme_udp_type)

static Scheme_Object *tcp_addresses(int argc, Scheme_Object *argv[])
{
#ifdef USE_TCP
  tcp_t socket = 0;
  Scheme_Tcp *tcp = NULL;
  int closed = 0;
  Scheme_Object *result[4];
  int with_ports = 0;
  int listener = 0;
  int udp = 0;

  if (SCHEME_OUTPUT_PORTP(argv[0])) {
    Scheme_Output_Port *op;
    op = scheme_output_port_record(argv[0]);
    if (op->sub_type == scheme_tcp_output_port_type)
      tcp = op->port_data;
    closed = op->closed;
  } else if (SCHEME_INPUT_PORTP(argv[0])) {
    Scheme_Input_Port *ip;
    ip = scheme_input_port_record(argv[0]);
    if (ip->sub_type == scheme_tcp_input_port_type)
      tcp = ip->port_data;
    closed = ip->closed;
  }

  if (argc > 1)
    with_ports = SCHEME_TRUEP(argv[1]);

  if (tcp) {
    socket = tcp->tcp;
  }
  else {
    if (SCHEME_LISTEN_PORTP(argv[0])) {
      listener = 1;
      socket = ((listener_t *)argv[0])->s[0];
    } else if (SCHEME_UDP_PORTP(argv[0])) {
      udp = 1;
      socket = ((Scheme_UDP *)argv[0])->s;
    } else {
      scheme_wrong_contract("tcp-addresses", "tcp-port?", 0, argc, argv);
    }
  }

  if (closed)
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "tcp-addresses: port is closed");

# ifdef USE_SOCKETS_TCP
  {
    unsigned int l;
    char here[MZ_SOCK_NAME_MAX_LEN], there[MZ_SOCK_NAME_MAX_LEN];
    char host_buf[MZ_SOCK_HOST_NAME_MAX_LEN];
    char svc_buf[MZ_SOCK_SVC_NAME_MAX_LEN];
    unsigned int here_len;
    unsigned int there_len = 0;
    int peerrc = 0;

    l = sizeof(here);
    if (getsockname(socket, (struct sockaddr *)here, &l)) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "tcp-addresses: could not get local address\n"
                       "  system error: %e",
		       SOCK_ERRNO());
    }
    here_len = l;

    if (!listener) {
      l = sizeof(there);
      peerrc = getpeername(socket, (struct sockaddr *)there, &l);
      if (peerrc && !udp) {
        scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                         "tcp-addresses: could not get peer address\n"
                         "  system error: %e", 
                         SOCK_ERRNO());
      }
      there_len = l;
    }

    scheme_getnameinfo((struct sockaddr *)here, here_len, 
		       host_buf, sizeof(host_buf),
                       (with_ports ? svc_buf : NULL), 
                       (with_ports ? sizeof(svc_buf) : 0));
    result[0] = scheme_make_utf8_string(host_buf);
    if (with_ports) {
      l = extract_svc_value(svc_buf);
      result[1] = scheme_make_integer(l);
    }

    if (listener || (udp && peerrc)) {
      result[with_ports ? 2 : 1] = scheme_make_utf8_string("0.0.0.0");
      result[3] = scheme_make_integer(0);
    }
    else {
      scheme_getnameinfo((struct sockaddr *)there, there_len, 
          host_buf, sizeof(host_buf),
          (with_ports ? svc_buf : NULL), 
          (with_ports ? sizeof(svc_buf) : 0));
      result[with_ports ? 2 : 1] = scheme_make_utf8_string(host_buf);
      if (with_ports) {
        l = extract_svc_value(svc_buf);
        result[3] = scheme_make_integer(l);
      }
    }
  }
# else
  result[0] = scheme_make_utf8_string("0.0.0.0");
  if (with_ports) {
    result[1] = scheme_make_integer(1);
    result[2] = result[0];
    result[3] = result[1];
  } else {
    result[1] = result[0];
  }
# endif

  return scheme_values(with_ports ? 4 : 2, result);
#else
  /* First arg can't possibly be right! */
  scheme_wrong_contract("tcp-addresses", "tcp-port?", 0, argc, argv);
#endif
}

static Scheme_Object *tcp_abandon_port(int argc, Scheme_Object *argv[])
{
#ifdef USE_TCP
  if (SCHEME_OUTPUT_PORTP(argv[0])) {
    Scheme_Output_Port *op;
    op = scheme_output_port_record(argv[0]);
    if (op->sub_type == scheme_tcp_output_port_type) {
      if (!op->closed) {
	((Scheme_Tcp *)op->port_data)->flags |= MZ_TCP_ABANDON_OUTPUT;
	scheme_close_output_port(argv[0]);
      }
      return scheme_void;
    }
  } else if (SCHEME_INPUT_PORTP(argv[0])) {
    /* Abandon is not really useful on input ports from the Racketeer's
       perspective, but it's here for completeness. */
    Scheme_Input_Port *ip;
    ip = scheme_input_port_record(argv[0]);
    if (ip->sub_type == scheme_tcp_input_port_type) {
      if (!ip->closed) {
	((Scheme_Tcp *)ip->port_data)->flags |= MZ_TCP_ABANDON_INPUT;
	scheme_close_input_port(argv[0]);
      }
      return scheme_void;
    }
  }
#endif

  scheme_wrong_contract("tcp-abandon-port", "tcp-port?", 0, argc, argv);

  return NULL;
}

void scheme_tcp_abandon_port(Scheme_Object *port) {
  tcp_abandon_port(1, &port);
}

static Scheme_Object *tcp_port_p(int argc, Scheme_Object *argv[])
{
#ifdef USE_TCP
  if (SCHEME_OUTPUT_PORTP(argv[0])) {
    Scheme_Output_Port *op;
    op = scheme_output_port_record(argv[0]);
    if (op->sub_type == scheme_tcp_output_port_type) {
      return scheme_true;
    }
  } else if (SCHEME_INPUT_PORTP(argv[0])) {
    Scheme_Input_Port *ip;
    ip = scheme_input_port_record(argv[0]);
    if (ip->sub_type == scheme_tcp_input_port_type) {
      return scheme_true;
    }
  }
#endif

  return scheme_false;
}


static Scheme_Object *tcp_accept_evt(int argc, Scheme_Object *argv[])
{
  Scheme_Object *r, *custodian;

  if (!SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_listener_type))
    scheme_wrong_contract("tcp-accept-evt", "tcp-listener?", 0, argc, argv);

  custodian = scheme_get_param(scheme_current_config(), MZCONFIG_CUSTODIAN);

  scheme_custodian_check_available((Scheme_Custodian *)custodian, "tcp-accept", "network");
  
  r = scheme_alloc_object();
  r->type = scheme_tcp_accept_evt_type;
  SCHEME_PTR1_VAL(r) = argv[0];
  SCHEME_PTR2_VAL(r) = custodian;

  return r;
}

static Scheme_Object *accept_failed(void *_msg, int argc, Scheme_Object **argv)
{
  scheme_raise_exn(MZEXN_FAIL_NETWORK, (char *)_msg);
  return NULL;
} 

static int tcp_check_accept_evt(Scheme_Object *ae, Scheme_Schedule_Info *sinfo)
{
  if (tcp_check_accept(SCHEME_PTR1_VAL(ae), NULL)) {
    Scheme_Object *a[2];
    char *fail_reason = NULL;
    a[0] = SCHEME_PTR1_VAL(ae);
    if (do_tcp_accept(1, a, SCHEME_PTR2_VAL(ae), &fail_reason)) {
      a[0] = scheme_current_thread->ku.multiple.array[0];
      a[1] = scheme_current_thread->ku.multiple.array[1];
      scheme_set_sync_target(sinfo, scheme_build_list(2, a), NULL, NULL, 0, 0, NULL);
      return 1;
    } else {
      /* error on accept */
      scheme_set_sync_target(sinfo, scheme_always_ready_evt, 
                             scheme_make_closed_prim(accept_failed, fail_reason),
                             NULL, 0, 0, NULL);
      return 1;
    }
  } else
    return 0;
}

static void tcp_accept_evt_needs_wakeup(Scheme_Object *ae, void *fds)
{
  tcp_accept_needs_wakeup(SCHEME_PTR1_VAL(ae), fds);
}

int scheme_get_port_socket(Scheme_Object *p, intptr_t *_s)
{
#ifdef USE_TCP
  tcp_t s = 0;
  int s_ok = 0;

  if (SCHEME_OUTPUT_PORTP(p)) {
    Scheme_Output_Port *op;
    op = scheme_output_port_record(p);
    if (op->sub_type == scheme_tcp_output_port_type) {
      if (!op->closed) {
	s = ((Scheme_Tcp *)op->port_data)->tcp;
	s_ok = 1;
      }
    }
  } else if (SCHEME_INPUT_PORTP(p)) {
    Scheme_Input_Port *ip;
    ip = scheme_input_port_record(p);
    if (ip->sub_type == scheme_tcp_input_port_type) {
      if (!ip->closed) {
	s = ((Scheme_Tcp *)ip->port_data)->tcp;
	s_ok = 1;
      }
    }
  }

  if (s_ok) {
    *_s = (intptr_t)s;
    return 1;
  } else
    return 0;
#endif
}

void scheme_socket_to_ports(intptr_t s, const char *name, int takeover,
                            Scheme_Object **_inp, Scheme_Object **_outp)
{
  Scheme_Tcp *tcp;
  Scheme_Object *v;

  tcp = make_tcp_port_data(s, takeover ? 2 : 3);

  v = make_tcp_input_port(tcp, name, NULL);
  *_inp = v;
  v = make_tcp_output_port(tcp, name, NULL);
  *_outp = v;
  
  if (takeover) {
    REGISTER_SOCKET(s);
  }
}

void scheme_socket_to_input_port(intptr_t s, Scheme_Object *name, int takeover,
                                 Scheme_Object **_inp)
{
  Scheme_Tcp *tcp;
  Scheme_Object *v;

  tcp = make_tcp_port_data(s, takeover ? 1 : 2);

  v = make_tcp_input_port_symbol_name(tcp, name, NULL);
  *_inp = v;
  
  if (takeover) {
    REGISTER_SOCKET(s);
  }
}

void scheme_socket_to_output_port(intptr_t s, Scheme_Object *name, int takeover,
                                  Scheme_Object **_outp)
{
  Scheme_Tcp *tcp;
  Scheme_Object *v;

  tcp = make_tcp_port_data(s, takeover ? 1 : 2);

  v = make_tcp_output_port_symbol_name(tcp, name, NULL);
  *_outp = v;
  
  if (takeover) {
    REGISTER_SOCKET(s);
  }
}

intptr_t scheme_dup_socket(intptr_t fd) {
#ifdef USE_SOCKETS_TCP
# ifdef USE_WINSOCK_TCP
  intptr_t nsocket;
  intptr_t rc;
  WSAPROTOCOL_INFO protocolInfo;
  rc = WSADuplicateSocket(fd, GetCurrentProcessId(), &protocolInfo);
  if (rc)
    return rc;
  nsocket = WSASocket(FROM_PROTOCOL_INFO, FROM_PROTOCOL_INFO, FROM_PROTOCOL_INFO, &protocolInfo, 0, WSA_FLAG_OVERLAPPED);
  REGISTER_SOCKET(nsocket);
  return nsocket;
# else
  intptr_t nfd;
  do {
    nfd = dup(fd);
  } while (nfd == -1 && errno == EINTR);
  return nfd;
# endif
#else
  return -1;
#endif
}

void scheme_close_socket_fd(intptr_t fd) 
{
#ifdef USE_SOCKETS_TCP
  UNREGISTER_SOCKET(fd);
  closesocket(fd);
  (void)scheme_fd_to_semaphore(fd, MZFD_REMOVE, 1);
#endif
}

/*========================================================================*/
/*                                 UDP                                    */
/*========================================================================*/

/* Based on a design and implemenation by Eduardo Cavazos. */

#ifdef UDP_IS_SUPPORTED

typedef struct Scheme_UDP_Evt {
  Scheme_Object so; /* scheme_udp_evt_type */
  Scheme_UDP *udp;
  short for_read, with_addr;
  int offset, len;
  char *str;
  char *dest_addr;
  int dest_addr_len;
} Scheme_UDP_Evt;

static int udp_close_it(Scheme_Object *_udp)
{
  Scheme_UDP *udp = (Scheme_UDP *)_udp;

  if (udp->s != INVALID_SOCKET) {
    closesocket(udp->s);
    (void)scheme_fd_to_semaphore(udp->s, MZFD_REMOVE, 1);
    udp->s = INVALID_SOCKET;

    scheme_remove_managed(udp->mref, (Scheme_Object *)udp);

    return 0;
  }

  return 1;
}

#endif

static Scheme_Object *make_udp(int argc, Scheme_Object *argv[])
{
#ifdef UDP_IS_SUPPORTED
  Scheme_UDP *udp;
  tcp_t s;
  char *address = "";
  unsigned short origid, id;

  TCP_INIT("udp-open-socket");

  if ((argc > 0) && !SCHEME_FALSEP(argv[0]) && !SCHEME_CHAR_STRINGP(argv[0]))
    scheme_wrong_contract("udp-open-socket", "(or/c string? #f)", 0, argc, argv);
  if ((argc > 1) && !SCHEME_FALSEP(argv[1]) && !CHECK_PORT_ID(argv[1]))
    scheme_wrong_contract("udp-open-socket", "(or/c " PORT_ID_TYPE " #f)", 1, argc, argv);

  if ((argc > 0) && SCHEME_TRUEP(argv[0])) {
    Scheme_Object *bs;
    bs = scheme_char_string_to_byte_string(argv[0]);
    address = SCHEME_BYTE_STR_VAL(bs);
  } else
    address = NULL;
  if ((argc > 1) && SCHEME_TRUEP(argv[1]))
    origid = (unsigned short)SCHEME_INT_VAL(argv[1]);
  else
    origid = 0;

  scheme_security_check_network("udp-open-socket", address, origid, 0);
  scheme_custodian_check_available(NULL, "udp-open-socket", "network");

  if (address || origid) {
    int err;
    GC_CAN_IGNORE struct mz_addrinfo *udp_bind_addr = NULL;
    if (!origid)
      origid = 1025;
    id = origid;
    udp_bind_addr = scheme_get_host_address(address, id, &err, -1, 1, 0);
    if (!udp_bind_addr) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-open-socket: can't resolve address\n"
                       "  address: %s\n"
                       "  system error: %N", 
		       address ? address : "<unspec>", 1, err);
      return NULL;
    }
    s = socket(udp_bind_addr->ai_family,
	       udp_bind_addr->ai_socktype,
	       udp_bind_addr->ai_protocol);
    mz_freeaddrinfo(udp_bind_addr);
  } else {
    s = socket(MZ_PF_INET, SOCK_DGRAM, 0);
  }

  if (s == INVALID_SOCKET) {
    int errid;
    errid = SOCK_ERRNO();
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "udp-open-socket: creation failed\n"
                     "  system error: %E", 
                     errid);
    return NULL;
  }

  udp = MALLOC_ONE_TAGGED(Scheme_UDP);
  udp->so.type = scheme_udp_type;
  udp->s = s;
  udp->bound = 0;
  udp->connected = 0;
  udp->previous_from_addr = NULL;

#ifdef USE_WINSOCK_TCP
  {
    unsigned long ioarg = 1;
    BOOL bc = 1;
    ioctlsocket(s, FIONBIO, &ioarg);
    setsockopt(s, SOL_SOCKET, SO_BROADCAST, (char *)(&bc), sizeof(BOOL));
  }
#else
  fcntl(s, F_SETFL, MZ_NONBLOCKING);
# ifdef SO_BROADCAST
  {
    int bc = 1;
    setsockopt(s, SOL_SOCKET, SO_BROADCAST, &bc, sizeof(bc));
  }
# endif
#endif

  {
    Scheme_Custodian_Reference *mref;
    mref = scheme_add_managed(NULL,
			      (Scheme_Object *)udp,
			      (Scheme_Close_Custodian_Client *)udp_close_it,
			      NULL,
			      1);
    udp->mref = mref;
  }

  return (Scheme_Object *)udp;
#else
  scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED,
		   "udp-open-socket: " NOT_SUPPORTED_STR);
  return NULL;
#endif
}

static Scheme_Object *
udp_close(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract("udp-close", "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  if (udp_close_it(argv[0])) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "udp-close: udp socket was already closed");
    return NULL;
  }
#endif

  return scheme_void;
}

static Scheme_Object *
udp_p(int argc, Scheme_Object *argv[])
{
  return (SCHEME_UDPP(argv[0]) ? scheme_true : scheme_false);
}

static Scheme_Object *
udp_bound_p(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract("udp-bound?", "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  return (((Scheme_UDP *)argv[0])->bound ? scheme_true : scheme_false);
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_connected_p(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract("udp-connected?", "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  return (((Scheme_UDP *)argv[0])->connected ? scheme_true : scheme_false);
#else
  return scheme_void;
#endif
}

#ifdef UDP_DISCONNECT_EADRNOTAVAIL_OK
# define OK_DISCONNECT_ERROR(e) (((e) == mz_AFNOSUPPORT) || ((e) == EADDRNOTAVAIL))
#else
# define OK_DISCONNECT_ERROR(e) ((e) == mz_AFNOSUPPORT)
#endif

static Scheme_Object *udp_bind_or_connect(const char *name, int argc, Scheme_Object *argv[], int do_bind)
{
  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract(name, "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp;
    char *address = NULL;
    unsigned short port = 0;
    GC_CAN_IGNORE struct mz_addrinfo *udp_bind_addr = NULL, *addr;

    udp = (Scheme_UDP *)argv[0];

    if (!SCHEME_FALSEP(argv[1]) && !SCHEME_CHAR_STRINGP(argv[1]))
      scheme_wrong_contract(name, "(or/c string? #f)", 1, argc, argv);
    if (do_bind && !CHECK_LISTEN_PORT_ID(argv[2]))
      scheme_wrong_contract(name, LISTEN_PORT_ID_TYPE, 2, argc, argv);
    if (!do_bind && !SCHEME_FALSEP(argv[2]) && !CHECK_PORT_ID(argv[2]))
      scheme_wrong_contract(name, "(or/c " PORT_ID_TYPE " #f)", 2, argc, argv);

    if (SCHEME_TRUEP(argv[1])) {
      Scheme_Object *bs;
      bs = scheme_char_string_to_byte_string(argv[1]);
      address = SCHEME_BYTE_STR_VAL(bs);
    }
    if (SCHEME_TRUEP(argv[2]))
      port = (unsigned short)SCHEME_INT_VAL(argv[2]);
    
    if (!do_bind && (SCHEME_TRUEP(argv[1]) != SCHEME_TRUEP(argv[2]))) {
      scheme_contract_error(name,
                            "last second and third arguments must be both #f or both non-#f",
                            "second argument", 1, argv[1], 
                            "third argument", 1, argv[2],
                            NULL);
    }

    scheme_security_check_network(name, address, port, !do_bind);

    if (udp->s == INVALID_SOCKET) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                       "%s: udp socket was already closed\n"
                       "  socket: %V", 
                       name, udp); 
      return NULL;
    }
    if (do_bind && udp->bound) { 
      scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                       "%s: udp socket is already bound\n"
                       "  socket: %V", 
                       name, udp);
      return NULL;
    }

    if (SCHEME_FALSEP(argv[1]) && SCHEME_FALSEP(argv[2])) {
      /* DISCONNECT */
      int errid = 0;
      if (udp->connected) {
        int ok;
#ifdef USE_NULL_TO_DISCONNECT_UDP
        ok = !connect(udp->s, NULL, 0);
#else
        GC_CAN_IGNORE mz_unspec_address ua;
        ua.sin_family = AF_UNSPEC;
        ua.sin_port = 0;
        memset(&(ua.sin_addr), 0, sizeof(ua.sin_addr));
        memset(&(ua.sin_zero), 0, sizeof(ua.sin_zero));
        ok = !connect(udp->s, (struct sockaddr *)&ua, sizeof(ua));
#endif
        if (!ok) errid = SOCK_ERRNO();
        if (ok || OK_DISCONNECT_ERROR(errid)) {
          udp->connected = 0;
          return scheme_void;
        }
        else {
          scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                           "%s: can't disconnect\n"
                           "  address: %s\n"
                           "  port number: %d\n"
                           "  system error: %E",
                           name, 
                           port, address ? address : "#f", 
                           errid);
        }
      }
      return scheme_void;
    }

    {
      /* RESOLVE ADDRESS */
      int err;
      udp_bind_addr = scheme_get_host_address(address, port, &err, -1, do_bind, 0);
      if (!udp_bind_addr) {
        scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                         "%s: can't resolve address\n"
                         "  address: %s\n"
                         "  system error: %N", 
                         name, 
                         address, 
                         1, err);
        return NULL;
      }
    }

    if (!do_bind) {
      /* CONNECT CASE */
      int ok, errid = -1;

      /* connect using first address that works: */
      for (addr = udp_bind_addr; addr; addr = addr->ai_next) {
        ok = !connect(udp->s, addr->ai_addr, addr->ai_addrlen);
        if (ok) {
          udp->connected = 1;
          mz_freeaddrinfo(udp_bind_addr);
          return scheme_void;
        } else
          errid = SOCK_ERRNO();
      }

      mz_freeaddrinfo(udp_bind_addr);

      scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                       "%s: can't connect\n"
                       "  address: %s\n"
                       "  port number: %d\n"
                       "  system error: %E", 
                       name, 
                       address ? address : "#f", 
                       port, 
                       errid);

      return NULL;
    } else {
      /* BIND CASE */
      int ok, errid = -1;

      if ((argc > 3) && SCHEME_TRUEP(argv[3])) {
	int one = 1;
	if (setsockopt(udp->s, SOL_SOCKET, SO_REUSEADDR, (void *) &one, sizeof(one))) {
	  scheme_raise_exn(MZEXN_FAIL_NETWORK,
			   "%s: can't set SO_REUSEADDR\n"
			   "  system error: %E",
			   name,
			   SOCK_ERRNO());
	  return NULL;
	}
      }

      /* bind using first address that works: */
      for (addr = udp_bind_addr; addr; addr = addr->ai_next) {
        ok = !bind(udp->s, addr->ai_addr, addr->ai_addrlen);
        if (ok) {
          udp->bound = 1;
          mz_freeaddrinfo(udp_bind_addr);
          return scheme_void;
        } else
          errid = SOCK_ERRNO();
      }

      mz_freeaddrinfo(udp_bind_addr);

      scheme_raise_exn(MZEXN_FAIL_NETWORK, 
                       "%s: can't bind\n"
                       "  address: %s\n"
                       "  port number: %d\n"
                       "  system error: %E",
                       name, 
                       address ? address : "#f", 
                       port, 
                       errid);
      return NULL;
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *udp_bind(int argc, Scheme_Object *argv[])
{
  return udp_bind_or_connect("udp-bind!", argc, argv, 1);
}

static Scheme_Object *udp_connect(int argc, Scheme_Object *argv[])
{
  return udp_bind_or_connect("udp-connect!", argc, argv, 0);
}

#ifdef UDP_IS_SUPPORTED

static int udp_check_send(Scheme_Object *_udp, Scheme_Schedule_Info *sinfo)
{
  Scheme_UDP *udp = (Scheme_UDP *)_udp;

  if (udp->s == INVALID_SOCKET)
    return 1;

  if (!sinfo || !sinfo->is_poll) {
    if (!check_fd_sema(udp->s, MZFD_CHECK_WRITE, sinfo, NULL))
      return 0;
  }

# ifdef HAVE_POLL_SYSCALL
  {
    GC_CAN_IGNORE struct pollfd pfd[1];
    int sr;

    pfd[0].fd = udp->s;
    pfd[0].events = POLLOUT;
    do {
      sr = poll(pfd, 1, 0);
    } while ((sr == -1) && (errno == EINTR));

    if (sr)
      return sr;
  }
# else
  {
    DECL_OS_FDSET(writefds);
    DECL_OS_FDSET(exnfds);
    struct timeval time = {0, 0};
    int sr;
    
    INIT_DECL_OS_WR_FDSET(writefds);
    INIT_DECL_OS_ER_FDSET(exnfds);
    
    MZ_OS_FD_ZERO(writefds);
    MZ_OS_FD_SET(udp->s, writefds);
    MZ_OS_FD_ZERO(exnfds);
    MZ_OS_FD_SET(udp->s, exnfds);
    
    do {
      sr = select(udp->s + 1, NULL, writefds, exnfds, &time);
    } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));
   
    if (sr)
      return sr;
  }
#endif

  check_fd_sema(udp->s, MZFD_CREATE_WRITE, sinfo, NULL);
  
  return 0;
}

static void udp_send_needs_wakeup(Scheme_Object *_udp, void *fds)
{
  Scheme_UDP *udp = (Scheme_UDP *)_udp;
  void *fds1, *fds2;
  tcp_t s = udp->s;
  
  fds1 = MZ_GET_FDSET(fds, 1);
  fds2 = MZ_GET_FDSET(fds, 2);
  
  MZ_FD_SET(s, (fd_set *)fds1);
  MZ_FD_SET(s, (fd_set *)fds2);
}

#endif

static Scheme_Object *do_udp_send_it(const char *name, Scheme_UDP *udp,
				     char *bstr, intptr_t start, intptr_t end,
				     char *dest_addr, int dest_addr_len, int can_block)
{
  intptr_t x;
  int errid = 0;

  while (1) {
    if (udp->s == INVALID_SOCKET) {
      /* socket was closed, maybe while we slept */
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: udp socket is closed\n"
                       "  socket: %V",
		       name, udp);
      return NULL;
    }
    if ((!dest_addr && !udp->connected)
	|| (dest_addr && udp->connected)) {
      /* socket is unconnected, maybe disconnected while we slept */
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: udp socket is%s connected\n"
                       "  socket: %V",
		       name, 
		       dest_addr ? "" : " not",
		       udp);
      return NULL;
    }

    udp->bound = 1; /* in case it's not bound already, send[to] binds it */

    if (dest_addr)
      x = sendto(udp->s, bstr XFORM_OK_PLUS start, end - start, 
		 0, (struct sockaddr *)dest_addr, dest_addr_len);
    else
      x = send(udp->s, bstr XFORM_OK_PLUS start, end - start, 0);

    if (x == -1) {
      errid = SOCK_ERRNO();
      if (WAS_EAGAIN(errid)) {
	if (can_block) {
	  /* Block and eventually try again. */
          Scheme_Object *sema;
          sema = scheme_fd_to_semaphore(udp->s, MZFD_CREATE_WRITE, 1);
          if (sema)
            scheme_wait_sema(sema, 0);
          else
            scheme_block_until((Scheme_Ready_Fun)udp_check_send, 
                               udp_send_needs_wakeup, 
                               (Scheme_Object *)udp, 
                               0);
	} else
	  return scheme_false;
      } else if (NOT_WINSOCK(errid) != EINTR)
	break;
    } else if (x != (end - start)) {
      /* this isn't supposed to happen: */
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: didn't send enough (%d != %d)", 
		       name,
		       x, end - start);
      return NULL;
    } else
      break;
  }
    
  if (x > -1) {
    return (can_block ? scheme_void : scheme_true);
  } else {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "%s: send failed\n"
                     "  system error: %E", 
		     name,
		     errid);
    return NULL;
  }
}

static Scheme_Object *udp_send_it(const char *name, int argc, Scheme_Object *argv[],
				  int with_addr, int can_block, Scheme_UDP_Evt *fill_evt)
{
#ifdef UDP_IS_SUPPORTED
  Scheme_UDP *udp;
  char *address = "";
  intptr_t start, end;
  int delta, err;
  unsigned short origid, id;
  GC_CAN_IGNORE struct mz_addrinfo *udp_dest_addr;

  udp = (Scheme_UDP *)argv[0];
#endif

  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract(name, "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  if (with_addr) {
    if (!SCHEME_CHAR_STRINGP(argv[1]))
      scheme_wrong_contract(name, "string?", 1, argc, argv);
    if (!CHECK_PORT_ID(argv[2]))
      scheme_wrong_contract(name, PORT_ID_TYPE, 2, argc, argv);
    delta = 0;
  } else
    delta = -2;

  if (!SCHEME_BYTE_STRINGP(argv[3 + delta]))
    scheme_wrong_contract(name, "bytes?", 3 + delta, argc, argv);
  
  scheme_get_substring_indices(name, argv[3 + delta], 
			       argc, argv,
			       4 + delta, 5 + delta, &start, &end);

  if (with_addr) {
    Scheme_Object *bs;
    bs = scheme_char_string_to_byte_string(argv[1]);
    address = SCHEME_BYTE_STR_VAL(bs);
    origid = (unsigned short)SCHEME_INT_VAL(argv[2]);

    scheme_security_check_network(name, address, origid, 1);

    id = origid;
  } else {
    address = NULL;
    id = origid = 0;
  }

  if (with_addr)
    udp_dest_addr = scheme_get_host_address(address, id, &err, -1, 0, 0);
  else
    udp_dest_addr = NULL;

  if (!with_addr || udp_dest_addr) {
    if (fill_evt) {
      char *s;
      fill_evt->str = SCHEME_BYTE_STR_VAL(argv[3+delta]);
      fill_evt->offset = start;
      fill_evt->len = end - start;
      if (udp_dest_addr) {
	s = (char *)scheme_malloc_atomic(udp_dest_addr->ai_addrlen);
	memcpy(s, udp_dest_addr->ai_addr, udp_dest_addr->ai_addrlen);
	fill_evt->dest_addr = s;
	fill_evt->dest_addr_len = udp_dest_addr->ai_addrlen;
	mz_freeaddrinfo(udp_dest_addr);
      }
      return scheme_void;
    } else {
      Scheme_Object *r;
      r = do_udp_send_it(name, udp,
			 SCHEME_BYTE_STR_VAL(argv[3+delta]), start, end,
			 (udp_dest_addr ? (char *)udp_dest_addr->ai_addr : NULL),
			 (udp_dest_addr ? udp_dest_addr->ai_addrlen : 0),
			 can_block);
      if (udp_dest_addr)
	mz_freeaddrinfo(udp_dest_addr);
      return r;
    }
  } else {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "%s: can't resolve address\n"
                     "  address: %s\n"
                     "  system error: %N", 
		     name,
		     address, 1, err);
    return NULL;
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *udp_send_to(int argc, Scheme_Object *argv[])
{
  return udp_send_it("udp-send-to", argc, argv, 1, 1, NULL);
}

static Scheme_Object *udp_send(int argc, Scheme_Object *argv[])
{
  return udp_send_it("udp-send", argc, argv, 0, 1, NULL);
}

static Scheme_Object *udp_send_to_star(int argc, Scheme_Object *argv[])
{
  return udp_send_it("udp-send-to*", argc, argv, 1, 0, NULL);
}

static Scheme_Object *udp_send_star(int argc, Scheme_Object *argv[])
{
  return udp_send_it("udp-send*", argc, argv, 0, 0, NULL);
}

static Scheme_Object *udp_send_to_enable_break(int argc, Scheme_Object *argv[])
{
  return scheme_call_enable_break(udp_send_to, argc, argv);
}

static Scheme_Object *udp_send_enable_break(int argc, Scheme_Object *argv[])
{
  return scheme_call_enable_break(udp_send, argc, argv);
}

#ifdef UDP_IS_SUPPORTED

static int udp_check_recv(Scheme_Object *_udp, Scheme_Schedule_Info *sinfo)
{
  Scheme_UDP *udp = (Scheme_UDP *)_udp;

  if (udp->s == INVALID_SOCKET)
    return 1;

  if (!sinfo || !sinfo->is_poll) {
    if (!check_fd_sema(udp->s, MZFD_CHECK_READ, sinfo, NULL))
      return 0;
  }

# ifdef HAVE_POLL_SYSCALL
  {
    GC_CAN_IGNORE struct pollfd pfd[1];
    int sr;

    pfd[0].fd = udp->s;
    pfd[0].events = POLLIN;
    do {
      sr = poll(pfd, 1, 0);
    } while ((sr == -1) && (errno == EINTR));

    if (sr)
      return sr;
  }
# else
  {
    DECL_OS_FDSET(readfds);
    DECL_OS_FDSET(exnfds);
    struct timeval time = {0, 0};
    int sr;
    
    INIT_DECL_OS_RD_FDSET(readfds);
    INIT_DECL_OS_ER_FDSET(exnfds);
    
    MZ_OS_FD_ZERO(readfds);
    MZ_OS_FD_SET(udp->s, readfds);
    MZ_OS_FD_ZERO(exnfds);
    MZ_OS_FD_SET(udp->s, exnfds);
    
    do {
      sr = select(udp->s + 1, readfds, NULL, exnfds, &time);
    } while ((sr == -1) && (NOT_WINSOCK(errno) == EINTR));
    
    if (sr)
      return sr;
  }
# endif

  check_fd_sema(udp->s, MZFD_CREATE_READ, sinfo, NULL);

  return 0;
}

static void udp_recv_needs_wakeup(Scheme_Object *_udp, void *fds)
{
  Scheme_UDP *udp = (Scheme_UDP *)_udp;
  void *fds1, *fds2;

  tcp_t s = udp->s;
  
  fds1 = MZ_GET_FDSET(fds, 0);
  fds2 = MZ_GET_FDSET(fds, 2);
  
  MZ_FD_SET(s, (fd_set *)fds1);
  MZ_FD_SET(s, (fd_set *)fds2);
}

#endif

static int do_udp_recv(const char *name, Scheme_UDP *udp, char *bstr, intptr_t start, intptr_t end, 
		       int can_block, Scheme_Object **v)
{
#ifdef UDP_IS_SUPPORTED
  intptr_t x;
  int errid = 0;
  char src_addr[MZ_SOCK_NAME_MAX_LEN];
  unsigned int asize = sizeof(src_addr);

  if (!udp->bound) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "%s: udp socket is not bound\n"
                     "  socket: %V",
		     name,
		     udp);
    return 0;
  }

  while (1) {
    if (udp->s == INVALID_SOCKET) {
      /* socket was closed, maybe while we slept */
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: udp socket is closed\n"
                       "  socket: %V",
		       name, udp);
      return 0;
    }

    {
      x = recvfrom(udp->s, bstr XFORM_OK_PLUS start, end - start, 0,
		   (struct sockaddr *)src_addr, &asize);
    }

    if (x == -1) {
      errid = SOCK_ERRNO();
      if (WAS_WSAEMSGSIZE(errid)) {
	x = end - start;
	errid = 0;
      } if (WAS_EAGAIN(errid)) {
	if (can_block) {
	  /* Block and eventually try again. */
          Scheme_Object *sema;
          sema = scheme_fd_to_semaphore(udp->s, MZFD_CREATE_READ, 1);
          if (sema)
            scheme_wait_sema(sema, 0);
          else
            scheme_block_until((Scheme_Ready_Fun)udp_check_recv, 
                               udp_recv_needs_wakeup, 
                               (Scheme_Object *)udp,
                               0);
	} else {
	  v[0] = scheme_false;
	  v[1] = scheme_false;
	  v[2] = scheme_false;
	  return 0;
	}
      } else if (NOT_WINSOCK(errid) != EINTR)
	break;
    } else
      break;
  }
  
  if (x > -1) {
    char host_buf[MZ_SOCK_HOST_NAME_MAX_LEN];
    char prev_buf[MZ_SOCK_HOST_NAME_MAX_LEN];
    char svc_buf[MZ_SOCK_SVC_NAME_MAX_LEN];
    int j, id;

    v[0] = scheme_make_integer(x);

    scheme_getnameinfo((struct sockaddr *)src_addr, asize,
		       host_buf, sizeof(host_buf),
		       svc_buf, sizeof(svc_buf));
    
    if (udp->previous_from_addr) {
      mzchar *s;
      s = SCHEME_CHAR_STR_VAL(udp->previous_from_addr);
      for (j = 0; s[j]; j++) {
	prev_buf[j] = (char)s[j];
      }
      prev_buf[j] = 0;
    }

    if (udp->previous_from_addr && !strcmp(prev_buf, host_buf)) {
      v[1] = udp->previous_from_addr;
    } else {
      Scheme_Object *vv;
      vv = scheme_make_immutable_sized_utf8_string(host_buf, -1);
      v[1] = vv;
      udp->previous_from_addr = v[1];
    }

    id = extract_svc_value(svc_buf);

    v[2] = scheme_make_integer(id);

    return 1;
  } else {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "%s: receive failed\n"
                     "  system error: %E",
		     name,
		     errid);
    return 0;
  }
#else
  return 0;
#endif
}

static Scheme_Object *udp_recv(const char *name, int argc, Scheme_Object *argv[], 
			       int can_block, Scheme_UDP_Evt *fill_evt)
{
  Scheme_UDP *udp;
  intptr_t start, end;
  Scheme_Object *v[3];

  udp = (Scheme_UDP *)argv[0];

  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract(name, "udp?", 0, argc, argv);
  if (!SCHEME_BYTE_STRINGP(argv[1]) || !SCHEME_MUTABLEP(argv[1]))
    scheme_wrong_contract(name, "(or/c bytes? (not/c immutable?))", 1, argc, argv);
  
  scheme_get_substring_indices(name, argv[1], 
			       argc, argv,
			       2, 3, &start, &end);
  if (fill_evt) {
    fill_evt->str = SCHEME_BYTE_STR_VAL(argv[1]);
    fill_evt->offset = start;
    fill_evt->len = end - start;
    return scheme_void;
  } else {
    do_udp_recv(name, udp, SCHEME_BYTE_STR_VAL(argv[1]), start, end, can_block, v);
    
    return scheme_values(3,v);
  }
}

static Scheme_Object *udp_receive(int argc, Scheme_Object *argv[])
{
  return udp_recv("udp-receive!", argc, argv, 1, NULL);
}

static Scheme_Object *udp_receive_star(int argc, Scheme_Object *argv[])
{
  return udp_recv("udp-receive!*", argc, argv, 0, NULL);
}

static Scheme_Object *udp_receive_enable_break(int argc, Scheme_Object *argv[])
{
  return scheme_call_enable_break(udp_receive, argc, argv);
}

static Scheme_Object *make_udp_evt(const char *name, int argc, Scheme_Object **argv, int for_read)
{
#ifdef UDP_IS_SUPPORTED
  Scheme_UDP_Evt *uw;
#endif

  if (!SCHEME_UDPP(argv[0]))
    scheme_wrong_contract(name, "udp?", 0, argc, argv);

#ifdef UDP_IS_SUPPORTED
  uw = MALLOC_ONE_TAGGED(Scheme_UDP_Evt);
  uw->so.type = scheme_udp_evt_type;
  uw->udp = (Scheme_UDP *)argv[0];
  uw->for_read = for_read;

  return (Scheme_Object *)uw;
#else
  return scheme_void;
#endif
}

static Scheme_Object *udp_read_ready_evt(int argc, Scheme_Object *argv[])
{
  return make_udp_evt("udp-receive-ready-evt", argc, argv, 1);
}

static Scheme_Object *udp_write_ready_evt(int argc, Scheme_Object *argv[])
{
  return make_udp_evt("udp-send-ready-evt", argc, argv, 0);
}

static Scheme_Object *udp_read_evt(int argc, Scheme_Object *argv[])
{
  Scheme_Object *evt;
  evt = make_udp_evt("udp-receive!-evt", argc, argv, 1);
  udp_recv("udp-receive!-evt", argc, argv, 0, (Scheme_UDP_Evt *)evt);
  return evt;
}

static Scheme_Object *udp_write_evt(int argc, Scheme_Object *argv[])
{
  Scheme_Object *evt;
  evt = make_udp_evt("udp-send-evt", argc, argv, 0);
  udp_send_it("udp-send-evt", argc, argv, 0, 0, (Scheme_UDP_Evt *)evt);
  return evt;
}

static Scheme_Object *udp_write_to_evt(int argc, Scheme_Object *argv[])
{
  Scheme_Object *evt;
  evt = make_udp_evt("udp-send-to-evt", argc, argv, 0);
  udp_send_it("udp-send-to-evt", argc, argv, 1, 0, (Scheme_UDP_Evt *)evt);
  ((Scheme_UDP_Evt *)evt)->with_addr = 1;
  return evt;
}

#ifdef UDP_IS_SUPPORTED
static int udp_evt_check_ready(Scheme_Object *_uw, Scheme_Schedule_Info *sinfo)
{
  Scheme_UDP_Evt *uw = (Scheme_UDP_Evt *)_uw;

  if (uw->for_read) {
    if (uw->str) {
      Scheme_Object *v[3];
      if (do_udp_recv("udp-receive!-evt", uw->udp, 
		      uw->str, uw->offset, uw->offset + uw->len, 
		      0, v)) {
	scheme_set_sync_target(sinfo, scheme_build_list(3, v), NULL, NULL, 0, 0, NULL);
	return 1;
      } else
	return 0;
    } else {
      return udp_check_recv((Scheme_Object *)uw->udp, NULL);
    }
  } else {
    if (uw->str) {
      Scheme_Object *r;
      r = do_udp_send_it("udp-send-evt", uw->udp, 
			 uw->str, uw->offset, uw->offset + uw->len, 
			 uw->dest_addr, uw->dest_addr_len,
			 0);
      if (SCHEME_TRUEP(r)) {
	scheme_set_sync_target(sinfo, scheme_void, NULL, NULL, 0, 0, NULL);
	return 1;
      } else
	return 0;
    } else
      return udp_check_send((Scheme_Object *)uw->udp, NULL);
  }
}

static void udp_evt_needs_wakeup(Scheme_Object *_uw, void *fds)
{
  Scheme_UDP_Evt *uw = (Scheme_UDP_Evt *)_uw;

  if (uw->for_read)
    udp_recv_needs_wakeup((Scheme_Object *)uw->udp, fds);
  else
    udp_send_needs_wakeup((Scheme_Object *)uw->udp, fds);
}
#endif

static int udp_check_open(char const *name, int argc, Scheme_Object *argv[]) {
  if (!SCHEME_UDPP(argv[0])) {
    scheme_wrong_contract(name, "udp?", 0, argc, argv);
    return 0; /* Why does no-one else expect control back after scheme_wrong_contract? */
    /* Or, conversely, why does everyone expect control back after scheme_raise_exn? */
  }

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];

    if (udp->s == INVALID_SOCKET) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
                       "%s: udp socket was already closed\n"
                       "  socket: %V",
                       name, udp);
      return 0;
    }

    return 1;
  }
#else
  return 0;
#endif
}

static Scheme_Object *
udp_multicast_loopback_p(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-loopback?", argc, argv))
    return NULL;

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    u_char loop;
    unsigned int loop_len = sizeof(loop);
    int status;
    status = getsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_LOOP, (void *) &loop, &loop_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-loopback?: getsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      return (loop ? scheme_true : scheme_false);
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_set_loopback(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-set-loopback!", argc, argv))
    return NULL;

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    u_char loop = SCHEME_TRUEP(argv[1]) ? 1 : 0;
    unsigned int loop_len = sizeof(loop);
    int status;
    status = setsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_LOOP, (void *) &loop, loop_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-set-loopback!: setsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      return scheme_void;
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_ttl(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-ttl", argc, argv))
    return NULL;

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    u_char ttl;
    unsigned int ttl_len = sizeof(ttl);
    int status;
    status = getsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_TTL, (void *) &ttl, &ttl_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-ttl: getsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      return scheme_make_integer(ttl);
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_set_ttl(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-set-ttl!", argc, argv))
    return NULL;
  if (!SCHEME_INTP(argv[1]) || (SCHEME_INT_VAL(argv[1]) < 0) || (SCHEME_INT_VAL(argv[1]) >= 256)) {
    scheme_wrong_contract("udp-multicast-set-ttl!", "byte?", 1, argc, argv);
    return NULL;
  }

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    u_char ttl = (u_char) SCHEME_INT_VAL(argv[1]);
    unsigned int ttl_len = sizeof(ttl);
    int status;
    status = setsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_TTL, (void *) &ttl, ttl_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-set-ttl!: setsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      return scheme_void;
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_interface(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-interface", argc, argv))
    return NULL;

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    GC_CAN_IGNORE struct in_addr intf;
    unsigned int intf_len = sizeof(intf);
    int status;
    status = getsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_IF, (void *) &intf, &intf_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-interface: getsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      char host_buf[MZ_SOCK_HOST_NAME_MAX_LEN];
      unsigned char *b = (unsigned char *) &intf; /* yes, this is in network order */
      sprintf(host_buf, "%d.%d.%d.%d", b[0], b[1], b[2], b[3]);
      return scheme_make_utf8_string(host_buf);
    }
  }
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_set_interface(int argc, Scheme_Object *argv[])
{
  if (!udp_check_open("udp-multicast-set-interface!", argc, argv))
    return NULL;
  if (!SCHEME_CHAR_STRINGP(argv[1]) && !SCHEME_FALSEP(argv[1])) {
    scheme_wrong_contract("udp-multicast-set-interface!", "(or/c string? #f)", 1, argc, argv);
    return NULL;
  }

#ifdef UDP_IS_SUPPORTED
  {
    Scheme_UDP *udp = (Scheme_UDP *) argv[0];
    GC_CAN_IGNORE struct in_addr intf;
    unsigned int intf_len = sizeof(intf);
    int status;

    if (SCHEME_FALSEP(argv[1])) {
      intf.s_addr = INADDR_ANY;
    } else {
      Scheme_Object *bs;
      char *address = "";
      GC_CAN_IGNORE struct mz_addrinfo *if_addr = NULL;
      int err;
      bs = scheme_char_string_to_byte_string(argv[1]);
      address = SCHEME_BYTE_STR_VAL(bs);
      if_addr = scheme_get_host_address(address, -1, &err, MZ_PF_INET, 0, 0);
      if (!if_addr) {
	scheme_raise_exn(MZEXN_FAIL_NETWORK,
			 "udp-multicast-set-interface!: can't resolve interface address\n"
			 "  address: %s\n"
			 "  system error: %N",
			 address ? address : "<unspec>", 1, err);
	return NULL;
      }
      intf = ((struct sockaddr_in *)if_addr->ai_addr)->sin_addr;
      mz_freeaddrinfo(if_addr);
    }

    status = setsockopt(udp->s, IPPROTO_IP, IP_MULTICAST_IF, (void *) &intf, intf_len);
    if (status)
      status = SOCK_ERRNO();
    if (status) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "udp-multicast-set-interface!: setsockopt failed\n"
		       "  system error: %N",
		       0, status);
      return NULL;
    } else {
      return scheme_void;
    }
  }
#else
  return scheme_void;
#endif
}

#ifdef UDP_IS_SUPPORTED

static Scheme_Object *
do_udp_multicast_join_or_leave_group(char const *name, int optname, Scheme_UDP *udp, Scheme_Object *multiaddrname, Scheme_Object *ifaddrname)
{
  GC_CAN_IGNORE struct ip_mreq mreq;
  unsigned int mreq_len = sizeof(mreq);
  int status;

  if (SCHEME_FALSEP(ifaddrname)) {
    mreq.imr_interface.s_addr = INADDR_ANY;
  } else {
    Scheme_Object *bs;
    char *address = "";
    GC_CAN_IGNORE struct mz_addrinfo *if_addr = NULL;
    int err;
    bs = scheme_char_string_to_byte_string(ifaddrname);
    address = SCHEME_BYTE_STR_VAL(bs);
    if_addr = scheme_get_host_address(address, -1, &err, MZ_PF_INET, 0, 0);
    if (!if_addr) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: can't resolve interface address\n"
		       "  address: %s\n"
		       "  system error: %N",
		       name, address ? address : "<unspec>", 1, err);
      return NULL;
    }
    mreq.imr_interface = ((struct sockaddr_in *)if_addr->ai_addr)->sin_addr;
    mz_freeaddrinfo(if_addr);
  }

  {
    Scheme_Object *bs;
    char *address = "";
    GC_CAN_IGNORE struct mz_addrinfo *group_addr = NULL;
    int err;
    bs = scheme_char_string_to_byte_string(multiaddrname);
    address = SCHEME_BYTE_STR_VAL(bs);
    group_addr = scheme_get_host_address(address, -1, &err, MZ_PF_INET, 0, 0);
    if (!group_addr) {
      scheme_raise_exn(MZEXN_FAIL_NETWORK,
		       "%s: can't resolve group address\n"
		       "  address: %s\n"
		       "  system error: %N",
		       name, address ? address : "<unspec>", 1, err);
      return NULL;
    }
    mreq.imr_multiaddr = ((struct sockaddr_in *)group_addr->ai_addr)->sin_addr;
    mz_freeaddrinfo(group_addr);
  }

  status = setsockopt(udp->s, IPPROTO_IP, optname, (void *) &mreq, mreq_len);
  if (status)
    status = SOCK_ERRNO();
  if (status) {
    scheme_raise_exn(MZEXN_FAIL_NETWORK,
		     "%s: setsockopt failed\n"
		     "  system error: %N",
		     name, 0, status);
    return NULL;
  } else {
    return scheme_void;
  }
}

#endif

static Scheme_Object *
udp_multicast_join_or_leave_group(char const *name, int optname, int argc, Scheme_Object *argv[])
{
  if (!udp_check_open(name, argc, argv))
    return NULL;
  if (!SCHEME_CHAR_STRINGP(argv[1])) {
    scheme_wrong_contract(name, "string?", 1, argc, argv);
    return NULL;
  }
  if (!SCHEME_CHAR_STRINGP(argv[2]) && !SCHEME_FALSEP(argv[2])) {
    scheme_wrong_contract(name, "(or/c string? #f)", 2, argc, argv);
    return NULL;
  }

#ifdef UDP_IS_SUPPORTED
  return do_udp_multicast_join_or_leave_group(name, optname,
					      (Scheme_UDP *) argv[0], argv[1], argv[2]);
#else
  return scheme_void;
#endif
}

static Scheme_Object *
udp_multicast_join_group(int argc, Scheme_Object *argv[])
{
  return udp_multicast_join_or_leave_group("udp-multicast-join-group!",
					   IP_ADD_MEMBERSHIP,
					   argc,
					   argv);
}

static Scheme_Object *
udp_multicast_leave_group(int argc, Scheme_Object *argv[])
{
  return udp_multicast_join_or_leave_group("udp-multicast-leave-group!",
					   IP_DROP_MEMBERSHIP,
					   argc,
					   argv);
}

/*========================================================================*/
/*                       precise GC traversers                            */
/*========================================================================*/

#ifdef MZ_PRECISE_GC

START_XFORM_SKIP;

#include "mzmark_network.inc"

static void register_traversers(void)
{
#ifdef USE_TCP
  GC_REG_TRAV(scheme_rt_tcp, mark_tcp);
# ifdef UDP_IS_SUPPORTED
  GC_REG_TRAV(scheme_udp_type, mark_udp);
  GC_REG_TRAV(scheme_udp_evt_type, mark_udp_evt);
# endif
#endif
  GC_REG_TRAV(scheme_listener_type, mark_listener);  
}

END_XFORM_SKIP;

#endif

#endif /* !NO_TCP_SUPPORT */
