2022-05-03_release-a-port-immediately.md

Release a port immediately

Use the socket.SO_REUSEADDR flag when creating a TCP server so that killing the server immediataly releases the port. Without a quick restart can error out with a "port already in use" error, and this can be SUPER annoying!

Example how to set the flag in python:

server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

And in C:

int enable = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int)) < 0)
    error("setsockopt(SO_REUSEADDR) failed");

Links:

• https://mobile.twitter.com/zeroprimezero/status/1271837883406712832
• https://stackoverflow.com/questions/24194961/how-do-i-use-setsockoptso-reuseaddr