linux recv() function flag parameter?

What will happen if I use recv(sockfd, buffer, len, 0); on a non-blocking socket?

If the socket sockfd is closed or nothing to be read, does the 开发者_如何学Crecv() block? (note: the flag in recv () is 0).

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If the socket is marked non blocking, recv will never block. period.

If the socket is fine but there is no data to be read you will get -1 as return value and errno will be set to EAGAIN.

If there is an error (closed socket etc.), you still get a -1 return value but errno will be set to the appropriate value.

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If there is nothing to read it will block, if the socket is closed it will return with an error.

See the recv man page.