diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
new file mode 100644
index 31ade0b..f674372
*** a/src/backend/libpq/auth.c
--- b/src/backend/libpq/auth.c
*************** ident_inet(hbaPort *port)
*** 1453,1459 ****
  
  	sock_fd = socket(ident_serv->ai_family, ident_serv->ai_socktype,
  					 ident_serv->ai_protocol);
! 	if (sock_fd < 0)
  	{
  		ereport(LOG,
  				(errcode_for_socket_access(),
--- 1453,1459 ----
  
  	sock_fd = socket(ident_serv->ai_family, ident_serv->ai_socktype,
  					 ident_serv->ai_protocol);
! 	if (sock_fd == PGINVALID_SOCKET)
  	{
  		ereport(LOG,
  				(errcode_for_socket_access(),
*************** ident_inet(hbaPort *port)
*** 1533,1539 ****
  					ident_response)));
  
  ident_inet_done:
! 	if (sock_fd >= 0)
  		closesocket(sock_fd);
  	pg_freeaddrinfo_all(remote_addr.addr.ss_family, ident_serv);
  	pg_freeaddrinfo_all(local_addr.addr.ss_family, la);
--- 1533,1539 ----
  					ident_response)));
  
  ident_inet_done:
! 	if (sock_fd != PGINVALID_SOCKET)
  		closesocket(sock_fd);
  	pg_freeaddrinfo_all(remote_addr.addr.ss_family, ident_serv);
  	pg_freeaddrinfo_all(local_addr.addr.ss_family, la);
*************** CheckRADIUSAuth(Port *port)
*** 2351,2357 ****
  	packet->length = htons(packet->length);
  
  	sock = socket(serveraddrs[0].ai_family, SOCK_DGRAM, 0);
! 	if (sock < 0)
  	{
  		ereport(LOG,
  				(errmsg("could not create RADIUS socket: %m")));
--- 2351,2357 ----
  	packet->length = htons(packet->length);
  
  	sock = socket(serveraddrs[0].ai_family, SOCK_DGRAM, 0);
! 	if (sock == PGINVALID_SOCKET)
  	{
  		ereport(LOG,
  				(errmsg("could not create RADIUS socket: %m")));
diff --git a/src/backend/libpq/ip.c b/src/backend/libpq/ip.c
new file mode 100644
index 7e8fc78..4db64fb
*** a/src/backend/libpq/ip.c
--- b/src/backend/libpq/ip.c
*************** pg_foreach_ifaddr(PgIfAddrCallback callb
*** 670,676 ****
  				total;
  
  	sock = socket(AF_INET, SOCK_DGRAM, 0);
! 	if (sock == -1)
  		return -1;
  
  	while (n_buffer < 1024 * 100)
--- 670,676 ----
  				total;
  
  	sock = socket(AF_INET, SOCK_DGRAM, 0);
! 	if (sock == PGINVALID_SOCKET)
  		return -1;
  
  	while (n_buffer < 1024 * 100)
*************** pg_foreach_ifaddr(PgIfAddrCallback callb
*** 711,717 ****
  #ifdef HAVE_IPV6
  	/* We'll need an IPv6 socket too for the SIOCGLIFNETMASK ioctls */
  	sock6 = socket(AF_INET6, SOCK_DGRAM, 0);
! 	if (sock6 == -1)
  	{
  		free(buffer);
  		close(sock);
--- 711,717 ----
  #ifdef HAVE_IPV6
  	/* We'll need an IPv6 socket too for the SIOCGLIFNETMASK ioctls */
  	sock6 = socket(AF_INET6, SOCK_DGRAM, 0);
! 	if (sock6 == PGINVALID_SOCKET)
  	{
  		free(buffer);
  		close(sock);
*************** pg_foreach_ifaddr(PgIfAddrCallback callb
*** 788,797 ****
  	char	   *ptr,
  			   *buffer = NULL;
  	size_t		n_buffer = 1024;
! 	int			sock;
  
  	sock = socket(AF_INET, SOCK_DGRAM, 0);
! 	if (sock == -1)
  		return -1;
  
  	while (n_buffer < 1024 * 100)
--- 788,797 ----
  	char	   *ptr,
  			   *buffer = NULL;
  	size_t		n_buffer = 1024;
! 	pgsocket	sock;
  
  	sock = socket(AF_INET, SOCK_DGRAM, 0);
! 	if (sock == PGINVALID_SOCKET)
  		return -1;
  
  	while (n_buffer < 1024 * 100)
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
new file mode 100644
index 1eae183..0179451
*** a/src/backend/libpq/pqcomm.c
--- b/src/backend/libpq/pqcomm.c
*************** StreamServerPort(int family, char *hostN
*** 392,398 ****
  				break;
  		}
  
! 		if ((fd = socket(addr->ai_family, SOCK_STREAM, 0)) < 0)
  		{
  			ereport(LOG,
  					(errcode_for_socket_access(),
--- 392,398 ----
  				break;
  		}
  
! 		if ((fd = socket(addr->ai_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
  		{
  			ereport(LOG,
  					(errcode_for_socket_access(),
*************** StreamConnection(pgsocket server_fd, Por
*** 632,638 ****
  	port->raddr.salen = sizeof(port->raddr.addr);
  	if ((port->sock = accept(server_fd,
  							 (struct sockaddr *) & port->raddr.addr,
! 							 &port->raddr.salen)) < 0)
  	{
  		ereport(LOG,
  				(errcode_for_socket_access(),
--- 632,638 ----
  	port->raddr.salen = sizeof(port->raddr.addr);
  	if ((port->sock = accept(server_fd,
  							 (struct sockaddr *) & port->raddr.addr,
! 							 &port->raddr.salen)) == PGINVALID_SOCKET)
  	{
  		ereport(LOG,
  				(errcode_for_socket_access(),
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
new file mode 100644
index e9072b7..cc844b9
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
*************** ConnCreate(int serverFd)
*** 2169,2175 ****
  
  	if (StreamConnection(serverFd, port) != STATUS_OK)
  	{
! 		if (port->sock >= 0)
  			StreamClose(port->sock);
  		ConnFree(port);
  		return NULL;
--- 2169,2175 ----
  
  	if (StreamConnection(serverFd, port) != STATUS_OK)
  	{
! 		if (port->sock != PGINVALID_SOCKET)
  			StreamClose(port->sock);
  		ConnFree(port);
  		return NULL;
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
new file mode 100644
index d53c41f..ec68be6
*** a/src/interfaces/libpq/fe-connect.c
--- b/src/interfaces/libpq/fe-connect.c
*************** keep_going:						/* We will come back to
*** 1632,1639 ****
  					conn->raddr.salen = addr_cur->ai_addrlen;
  
  					/* Open a socket */
! 					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
! 					if (conn->sock < 0)
  					{
  						/*
  						 * ignore socket() failure if we have more addresses
--- 1632,1654 ----
  					conn->raddr.salen = addr_cur->ai_addrlen;
  
  					/* Open a socket */
! 					{
! 						/*
! 						 * While we use 'pgsocket' as the socket type in the
! 						 * backend, we use 'int' for libpq socket values.
! 						 * This requires us to map PGINVALID_SOCKET to -1
! 						 * on Windows.
! 						 * See http://msdn.microsoft.com/en-us/library/windows/desktop/ms740516%28v=vs.85%29.aspx
! 						 */
! 						pgsocket sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
! #ifdef WIN32
! 						if (sock == PGINVALID_SOCKET)
! 							conn->sock = -1;
! 						else
! #endif
! 							conn->sock = sock;
! 					}
! 					if (conn->sock == -1)
  					{
  						/*
  						 * ignore socket() failure if we have more addresses
*************** internal_cancel(SockAddr *raddr, int be_
*** 3136,3142 ****
  				char *errbuf, int errbufsize)
  {
  	int			save_errno = SOCK_ERRNO;
! 	int			tmpsock = -1;
  	char		sebuf[256];
  	int			maxlen;
  	struct
--- 3151,3157 ----
  				char *errbuf, int errbufsize)
  {
  	int			save_errno = SOCK_ERRNO;
! 	pgsocket	tmpsock = PGINVALID_SOCKET;
  	char		sebuf[256];
  	int			maxlen;
  	struct
*************** internal_cancel(SockAddr *raddr, int be_
*** 3149,3155 ****
  	 * We need to open a temporary connection to the postmaster. Do this with
  	 * only kernel calls.
  	 */
! 	if ((tmpsock = socket(raddr->addr.ss_family, SOCK_STREAM, 0)) < 0)
  	{
  		strlcpy(errbuf, "PQcancel() -- socket() failed: ", errbufsize);
  		goto cancel_errReturn;
--- 3164,3170 ----
  	 * We need to open a temporary connection to the postmaster. Do this with
  	 * only kernel calls.
  	 */
! 	if ((tmpsock = socket(raddr->addr.ss_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
  	{
  		strlcpy(errbuf, "PQcancel() -- socket() failed: ", errbufsize);
  		goto cancel_errReturn;
*************** cancel_errReturn:
*** 3220,3226 ****
  				maxlen);
  		strcat(errbuf, "\n");
  	}
! 	if (tmpsock >= 0)
  		closesocket(tmpsock);
  	SOCK_ERRNO_SET(save_errno);
  	return FALSE;
--- 3235,3241 ----
  				maxlen);
  		strcat(errbuf, "\n");
  	}
! 	if (tmpsock != PGINVALID_SOCKET)
  		closesocket(tmpsock);
  	SOCK_ERRNO_SET(save_errno);
  	return FALSE;
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
new file mode 100644
index 22bbe4a..ee975d4
*** a/src/interfaces/libpq/libpq-int.h
--- b/src/interfaces/libpq/libpq-int.h
*************** struct pg_conn
*** 364,369 ****
--- 364,370 ----
  	PGnotify   *notifyTail;		/* newest unreported Notify msg */
  
  	/* Connection data */
+ 	/* See PQconnectPoll() for how we use 'int' and not 'pgsocket'. */
  	int			sock;			/* Unix FD for socket, -1 if not connected */
  	SockAddr	laddr;			/* Local address */
  	SockAddr	raddr;			/* Remote address */