Can a port be bound when the process has terminated?

If the original process spawns child processes, it's possible for the child processes to keep the socket open past the parent process exit. If the parent process is the only process with the socket open, it should clean up upon termination. An existing process will close all open file descriptors, which includes all its sockets.

Once a close is initiated, the socket may still be in TIME_WAIT state. TCP attempts to guarantee delivery of all data being transmitted. When a socket is closed, it goes into TIME_WAIT to fulfil this guarantee. There are multiple variables that may require some time if they're TCP sockets such as to finish handshaking or whether the sockets were configured with SO_LINGER option.

Here's a link that explains TIME_WAIT from the Unix Socket FAQ: http://www.developerweb.net/forum/showthread.php?t=2941

Darren Hall

Posted 2009-11-30T22:26:09.653

Reputation: 6 354

Welcome to the not-so-pretty side of TCP/IP. Many years back, I helped Addison Wesley as an editor for Stevens' books - Advanced Programming in the UNIX Environment and UNIX Network Programming - and helped improve the example programs with code to handle the edge cases such as the ones you're hitting. We did our best to document the situation, but that doesn't make the problem go away. Here's another good explanation: http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable

– pbr – 2009-12-01T21:11:34.843

Aborting a process will leave the sockets closing, going into TIME_WAIT and TIME_WAIT2 states. If the app is not written to make the sockets reusable, the port will still be bound when you try to start an app on that port. – Tim Williscroft – 2009-12-07T01:24:33.087

Can a port be bound when the process has terminated?

Answers