How to See If a Port Is Open on a PC?

By William Nagel

Applications on your computer connect to the Internet by using ports. Ports help prevent transmitted data from arriving at an incorrect destination and allow computer applications to exchange information directly. Most applications will open ports automatically when they connect to the Internet, but if you want to manually check to see which ports are open on your computer, you can use the built-in "netstat" command to view a list of active ports on your computer.

Things You'll Need

  • Active Internet connection

Step 1

Press "Windows + R" on your keyboard to open the "Run" dialog. Type "cmd" into the "Run" dialog and press "OK" to open a Command prompt.

Step 2

Type "netstat --a" into the Command prompt and press "Enter." The "netstat" command will run and output a list of information. The "Local Address" column is the column that identifies which ports are active.

Step 3

Examine the entries in the "Local Address" column, which displays a series of numbers. The numbers listed before the ":" are parts of your computer's address. The numbers listed after the ":" are the port numbers.

Step 4

Search the entries in the "Local Address" column for a specific port number, or browse the list to see which ports are open on your computer. If you suspect that a port should not be open, or if you don't know why a port is open, perform an Internet search to discover whether the connection is the result of a Trojan horse or virus on your computer.

Tips & Warnings

  • To automatically refresh the list of open ports, type "netstat --a X" and replace "X" with the number of seconds you want to pass between refreshes.

References & Resources