Entry

How can I free a port that has been used by a python server?

Sep 13th, 2000 15:17
Tomas V.V.Cox, unknown unknown, Johannes Stezenbach

Problem:

######################################################################
class Server (SocketServer.ThreadingMixIn,
              BaseHTTPServer.HTTPServer):
    pass
    
if __name__ == '__main__':

    port = 1729 # Called from interactive session, debug mode.

    proxy =  Server (('127.0.0.1', port), Handler)
    proxy.serve_forever ()
######################################################################
    
The problem is, when I run this more than once in interactive mode, I
get the error:

socket.error: (98, 'Address already in use')

Is there some way to free up port 1729 when proxy gets destroyed?

Solution:

Normally you should close the socket properly before exiting. You could 
try to catch KeyboardInterrupt or whatever signal you use to break out 
of serve_forever(), but it's problematic with multithreaded servers.

Workaround:
-----
class Server (SocketServer.ThreadingMixIn,
              BaseHTTPServer.HTTPServer):
    def server_bind(self):
        import socket
        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 
1)
        BaseHTTPServer.HTTPServer.server_bind(self)
-----

Note that this doesn't free up the port, instead it allows more than  
one process to bind to it, under certain circumstances (bind() still
fails if there's already a socket actively listening on that port).
See socket(7) (Linux) for details.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
An other thing you can do is wait (between 5 and 30 seconds) :)

Tomas V.V.Cox