12.5 Winsock如何支持读超时

https://scz.617.cn/network/200610101459.txt

A: scz@nsfocus

Winsock有个Windows独有的SO_RCVTIMEO选项:

---

int i = timeout;

if ( SOCKET_ERROR == setsockopt ( s, SOL_SOCKET, SO_RCVTIMEO, ( char * )&i, sizeof( i ) ) ) { ... ... }

---

如果碰上不支持SO_RCVTIMEO选项的情形，还可以利用select()实现读超时:

---

static int recv_with_timeout ( SOCKET s, char FAR *buf, int len, int flags, unsigned int timeout ) { int error; fd_set rset, eset; struct timeval tv; int ret = SOCKET_ERROR;

FD_ZERO( &rset );
FD_ZERO( &eset );
FD_SET( s, &rset );
FD_SET( s, &eset );
tv.tv_sec   = timeout;
tv.tv_usec  = 0;
error       = select( 0, &rset, NULL, &eset, timeout ? &tv : NULL );
if ( SOCKET_ERROR == error )
{
}
else if ( 0 == error )
{
}
else if ( FD_ISSET( s, &rset ) )
{
    ret = recv( s, buf, len, flags );
}
else
{
}
return( ret );

} / end of recv_with_timeout /

Q: 系统支持SO_RCVTIMEO选项，但实测下来读超时没有生效。

A: scz@nsfocus 2006-10-10 14:44

检查一下如何创建套接字的，要确保在重叠套接字上使用SO_RCVTIMEO选项:

---

SOCKET s;

if 1

s = socket( PF_INET, SOCK_STREAM, IPPROTO_TCP );

else

s = WSASocket ( PF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, WSA_FLAG_OVERLAPPED );

endif

if ( INVALID_SOCKET == s ) { ... ... }

---

非重叠套接字(non-overlapped socket)上SO_RCVTIMEO选项无效。