Closing a listening TCP socket in C

Question

Suppose you have a socket listening on a TCP port, and some clients are connected. When one issues sock_close(fd) in C and tries to bind again on the same port, binding fails. Some TIME_WAIT state is seen on the "netstat -plutnoa" such as:

tcp        0      0 127.0.0.1:4567          127.0.0.1:32977         TIME_WAIT   -                timewait (17.12/0/0)

So how one can properly disconnect the server socket and reconnect on the same port immediately?

I found SO_REUSEADDR, checking it now... – whoi Oct 04 '10 at 13:58 — whoi, Oct 04 '10 at 13:58

score 9 · Accepted Answer · edited Mar 26 '18 at 11:51

9

You want to use the SO_REUSEADDR option on the socket. The relevant manpage is socket(7). Here's an example of its usage. This question explains what happens.

edited Mar 26 '18 at 11:51

Sandburg

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answered Oct 04 '10 at 14:00

Matt Joiner

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A CloudFlare blog post may also supply some useful thoughts on SO_REUSEADDR. https://blog.cloudflare.com/its-crowded-in-here/ – Ron Burk Oct 02 '20 at 20:03

Closing a listening TCP socket in C

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