Here's a little multiuser chat server written for various POSIX-compatible operating systems. Written and tested on Mac OS X 10.6, but it should work on your favorite Linux, too.
Placed in public domain, use it for whatever you want (since it's so simple). 177 lines of pure C powah, dood.
Code follows after the break.
Just a warning.
Calling close() on listening socket in another thread will NOT prevent another connection from being made. Instead, you must call shutdown(). This should abort existing select() calls (probably accept() too, but I didn't try).
Guess how I found out 🙂
If you are impaired with Windows, and you want something similar to sshfs (that is, mount a remote system as a local drive) look no further:
It's originally Japanese, and suffers from a bit of Engrish, but it is free and obviously developed by a genius, so it's all forgiven.
Hiroki Asakawa, thank you!