I have a Python application which opens a simple TCP socket to communicate with another Python application on a separate host. Sometimes the program will either error or I will directly kill it, and in either case the socket may be left open for some unknown time.
The next time I go to run the program I get this error:
socket.error: [Errno 98] Address already in use
Now the program always tries to use the same port, so it appears as though it is still open. I checked and am quite sure the program isn't running in the background and yet my address is still in use.
SO, how can I manually (or otherwise) close a socket/address so that my program can immediately re-use it?
Update
Based on Mike's answer I checked out the socket(7)
page and looked at SO_REUSEADDR:
SO_REUSEADDR Indicates that the rules used in validating addresses supplied in a bind(2) call should allow reuse of local addresses. For AF_INET sockets this means that a socket may bind, except when there is an active listening socket bound to the address. When the listen‐ ing socket is bound to INADDR_ANY with a specific port then it is not possible to bind to this port for any local address. Argument is an integer boolean flag.
Assume your socket is named s
... you need to set socket.SO_REUSEADDR
on the server's socket before binding to an interface... this will allow you to immediately restart a TCP server...
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((ADDR, PORT))