Sometimes a port doesn't release properly resulting in servers staring on non-standard ports.
How do you release the port? Easy, use this:
lsof -i :portnumber
Grab the resulting PID and kill the process. Use
-9 if you really have to.
Here's a "worked example":
$ lsof -i :1990
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
java 2857 david 39u IPv6 0x23ed6292526f5971 0t0 TCP *:stun-p1 (LISTEN)
$ kill -9 2857