SocketServer.ThreadingTCPServer - Cannot bind to address after program restart

Question

As a follow-up to cannot-bind-to-address-after-socket-program-crashes, I was receiving this error after my program was restarted:

socket.error: [Errno 98] Address already in use

In this particular case, instead of using a socket directly, the program is starting its own threaded TCP server:

httpd = SocketServer.ThreadingTCPServer(('localhost', port), CustomHandler)
httpd.serve_forever()

How can I fix this error message?

score 20 · Answer 1 · answered Jun 29 '10 at 04:09

20

The above solution didn't work for me but this one did:

   SocketServer.ThreadingTCPServer.allow_reuse_address = True
   server = SocketServer.ThreadingTCPServer(("localhost", port), CustomHandler)
   server.serve_forever()

answered Jun 29 '10 at 04:09

Lynn

1,103
15
29

Interesting, what version of Python are you using? – Justin Ethier Jun 29 '10 at 13:13
same here, this works but not one with httpd.server_bind() Python 2.6.5 – rombarcz Jun 30 '10 at 15:11
Worked for me on Python 3.4.3, but Justin's answer did not. – Oliver Bock Sep 27 '15 at 04:29

score 16 · Accepted Answer · answered Feb 16 '10 at 16:17

In this particular case, .setsockopt(SOL_SOCKET, SO_REUSEADDR, 1) may be called from the TCPServer class when the allow_reuse_address option is set. So I was able to solve it as follows:

httpd = SocketServer.ThreadingTCPServer(('localhost', port), CustomHandler, False) # Do not automatically bind
httpd.allow_reuse_address = True # Prevent 'cannot bind to address' errors on restart
httpd.server_bind()     # Manually bind, to support allow_reuse_address
httpd.server_activate() # (see above comment)
httpd.serve_forever()

Anyway, thought this might be useful. The solution will differ slightly in Python 3.0

SocketServer.ThreadingTCPServer - Cannot bind to address after program restart

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