From 172f374a63bfc61f71ee925463927a81350b66da Mon Sep 17 00:00:00 2001 From: Sandro Tosi Date: Fri, 2 Sep 2011 20:06:31 +0200 Subject: [PATCH] #12781: Mention SO_REUSEADDR flag near socket examples --- Doc/library/socket.rst | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst index d462bb77480..64b41835220 100644 --- a/Doc/library/socket.rst +++ b/Doc/library/socket.rst @@ -1014,6 +1014,25 @@ the interface:: s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF) +Running an example several times with too small delay between executions, could +lead to this error:: + + socket.error: [Errno 98] Address already in use + +This is because the previous execution has left the socket in a ``TIME_WAIT`` +state, and can't be immediately reused. + +There is a :mod:`socket` flag to set, in order to prevent this, +:data:`socket.SO_REUSEADDR`:: + + s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) + s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + s.bind((HOST, PORT)) + +the :data:`SO_REUSEADDR` flag tells the kernel to reuse a local socket in +``TIME_WAIT`` state, without waiting for its natural timeout to expire. + + .. seealso:: For an introduction to socket programming (in C), see the following papers: