Using netstat to see the listening processes
To see if a program or process is listening on a port, ready to accept a packet, use the netstat program.
The arguments to the netstat program are listed below:
•t – Show TCP
•u – Show UDP
•l – Show only listening processes (netstat can show both listening and all established connections, i.e. as a client too)
•n – Do not resolve network IP address names or port numbers
•p – Show the process name that is listening on the port