linux-list-of-network-service-connections
lsof
or
lsof -Pnl | more
-P no port # to port name -n no network # to network name -l no user id to user name
netstat -tulpn
* -t : TCP port
* -u : UDP port
* -l : Show only listening sockets.
* -p : Show the PID and name of the program to which each socket / port belongs
* -n : No DNS lookup (speed up operation)
or netstat -npl
cat /etc/services