how do I find in C that a port is free to use?

Question

The OS is Linux. I have a server process that can change its port realtime. However I would like to know in advance if a port is free before binding.

Scenario: Server bi

Answer 1

This is an obvious race condition, since other processes on your system might be binding to ports in parallel. So, any solution you find will be imperfect, and you will still need to just write it according to the "try to bind(), if it fails pick a new port number and try again" approach.