How to Find the Link Between a Program and a Port

If you're using Linux, some (many?) distributions have a -p flag for their netstat program. BSD users are not so lucky. Fortunately, we have lsof.

Actually, anybody can have lsof. It is not a part of the default OpenBSD install, but can easily be installed as a binary package with the pkg_add program.

Just type:

$ sudo lsof | grep LISTEN

Your output will look like this:

python2.3  5196      root    5u  IPv4 0xd20d2af0       0t0   TCP *:6601 (LISTEN)
tcpserver  5858      root    3u  IPv4 0xd20d24b0       0t0   TCP *:www (LISTEN)
sshd       7050      root    4u  IPv6 0xd20d2000       0t0   TCP *:ssh (LISTEN)
sshd       7050      root    5u  IPv4 0xd20d2190       0t0   TCP *:ssh (LISTEN)
tcpserver 22594      root    3u  IPv4 0xd20d27d0       0t0   TCP *:imaps (LISTEN)

And you can then pair the open port with the program that is on that port.