Tested on mac.
Assuming you know the command name, own the process, and want to kill them all.
$ killall node
Based on: http://stackoverflow.com/questions/3855127
$ lsof -i tcp:5000
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
node 82240 davidlivingston 11u IPv6 0x136079696e382719 0t0 TCP *:commplex-main (LISTEN)
$ kill 82240