（recv（）== 0）表示断开连接或超时？ （套接字，Linux和Windows）

Question

我在阻塞套接字上设置了超时..

DWORD to = 1200;
if (setsockopt (soc, SOL_SOCKET, SO_RCVTIMEO, (char *)&to, sizeof(to))) {
    ...
}

如果recv（）然后返回零，我怎么能告诉这是链接断开或读取超时？如果不是我想读更多，如果它是discon我想采取其他行动。我意识到我可以删除t / o，然后我会知道它是discon，但我还需要定期监视读取过程的进展情况。

任何帮助非常感谢。干杯 - 丰富

Answer 1

来自SO_RCVTIMEO的手册页的socket部分：

...if no data has been transferred and the time‐out has been reached,
then -1 is returned with errno set to EAGAIN or EWOULDBLOCK, or
EINPROGRESS (for connect(2)) just as if the socket was specified to
be non‐blocking.

来自recv的手册页：

These calls return the number of bytes received, or -1 if an error
occurred.  In the event of an error, errno is set to indicate the
error.

When a stream socket peer has performed an orderly shutdown, the
return value will be 0 (the traditional "end-of-file" return).

Datagram sockets in various domains (e.g., the UNIX and Internet
domains) permit zero-length datagrams.  When such a datagram is
received, the return value is 0.

The value 0 may also be returned if the requested number of bytes to
receive from a stream socket was 0.

对recv的调用将在断开连接时返回0，或者如果收到零长度数据报，或者请求的字节数为0。

对recv的调用将返回-1任何错误，包括超时。您需要检查errno以区分超时与其他错误。