close() and shutdown()--Get outta my face!

Whew! You've been send()'ing and recv()'ing data all day long, and you've had it. You're ready to close the connection on your socket descriptor. This is easy. You can just use the regular Unix file descriptor close() function:

close(sockfd);

This will prevent any more reads and writes to the socket. Anyone attempting to read or write the socket on the remote end will receive an error.

Just in case you want a little more control over how the socket closes, you can use the shutdown() function. It allows you to cut off communication in a certain direction, or both ways (just like close() does.) Synopsis:

int shutdown(int sockfd, int how);

sockfd is the socket file descriptor you want to shutdown, and how is one of the following:

• 0 - Further receives are disallowed
• 1 - Further sends are disallowed
• 2 - Further sends and receives are disallowed (like close())

shutdown() returns 0 on success, and -1 on error (with errno set accordingly.)

If you deign to use shutdown() on unconnected datagram sockets, it will simply make the socket unavailable for further send() and recv() calls (remember that you can use these if you connect() your datagram socket.)

Nothing to it.

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Copyright © 1995, 1996 by Brian "Beej" Hall. This guide may be reprinted in any medium provided that its content is not altered, it is presented in its entirety, and this copyright notice remains intact. Contact beej@ecst.csuchico.edu for more information.