12.5 Winsock如何支持读超时

原文地址：http://www.opencjk.org/~scz/network/200610101459.txt

A: scz@nsfocus

Winsock有个Windows独有的SO_RCVTIMEO选项:

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

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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 */
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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:

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