On localhost, how do I pick a free port number?

user_166939 0
Viewed 161198

I'm trying to play with inter-process communication and since I could not figure out how to use named pipes under Windows I thought I'll use network sockets. Everything happens locally. The server is able to launch slaves in a separate process and listens on some port. The slaves do their work and submit the result to the master. How do I figure out which port is available? I assume I cannot listen on port 80 or 21?

I'm using Python, if that cuts the choices down.

port ipc sockets python
5 Answers

If you only need to find a free port for later use, here is a snippet similar to a previous answer, but shorter, using socketserver:

import socketserver

with socketserver.TCPServer(("localhost", 0), None) as s:
    free_port = s.server_address[1]

Note that the port is not guaranteed to remain free, so you may need to put this snippet and the code using it in a loop.

user_2002340
Related