Killing a Process Based On a Specific Port Number

netstat (network statistics) is a command-line tool that displays network connections (both incoming and outgoing), routing tables, and a number of network interface statistics. It is available on Unix, Unix-like, and Windows NT-based operating systems.
It is used for finding problems in the network and to determine the amount of traffic on the network as a performance measurement. [wikipedia.com]

Parameters used with netstat command are:

netstat /? Output

In case you want to kill a process without knowing its name and the only information you’ve got is a port number; there’s no need to worry about it. Here are the six simple steps in KILLING A PROCESS BASED ON A SPECIFIC PORT NUMBER.

1. Go to RUN and type cmd
2. Use netstat -aon | find ":port number" command to view a specific network port if it is in use or not. 
3. Go to Task Manager (Alt+Ctrl+Del)
4. Select Processes Tab
5. Check PID on view menu
6. Kill the process base on PID

If you want to change a port number, you may edit services file located on C:\WINDOWS\system32\drivers\etc

Common TCP and UDP Port Numbers

Port numbers are assigned to each services that run over transport protocols such as TCP and UDP ranging from 0 to 65535.

Port numbers are divided into three ranges:

0-1023: System Ports – assigned by IETF process, well-known port numbers
1024-49151: User Ports – are assigned by IANA, registered ports
49152-65535: Dynamic/Private Ports – not assigned, can be used by anyone

Port numbers 0 to 1023 are reserved for privelege and other prominent services.
Common port numbers include:

List of TCP port numbers

21: File Transfer Protocol [FTP]
22: Secure Shell [SSH]
23: Telnet remote login service
25: Simple Mail Transfer Protocol [SMTP]
80: Hypertext Transfer Protocol [HTTP]
110: Post Office Protocol [POP]
119: Network News Transfer Protocol [NNTP]
143: Internet Message Access Protocol [IMAP]
156: SQL Server
179: Border Gateway Protocol [BGP]
443: HTTP Secure [HTTPS]

List of UDP port numbers

53: Domain Name System [DNS]
67: Dynamic Host Configuration Protocol - Client [DHCP]
68: Dynamic Host Configuration Protocol - Server [DHCP]
69: Trivial File Transfer Protocol [TFTP]
161: Simple Network Management Protocol [SNMP]