How to tell what process has a specific port open on Linux?

netstat -lnp --inet inet -4 -6

lsof -i :123

Show ports and the applications bound to them

#!/bin/bash

netstat -lntup \

| awk '/^(tcp|udp)/ {print substr($4, match($4, ":[^:]+$") + 1) "/" $1, substr($NF, 1, index($NF, "/") - 1)}' \

| while read PORT PID

do

        BIN=$(readlink /proc/$PID/exe)

        echo $PORT $PID $BIN

done