Port Scanner determines lively services on the host using TCP port interrogations. Port Scanner will check which TCP ports are listening. You can test these ports to see if they are running. It is recommended that any services which are not necessary be disabled. Use Port Scanner to scan individual ports to determine if the device is listening on that port. Port Scanner will analyze given IP address or URL for open ports to help you to secure it.
You can check out the demo of port scanner on YouTube.
Below are the link of Port Scanner extension for Mozilla Firefox & Google Chrome
1) For Mozilla Firefox: https://addons.mozilla.org/en-US/firefox/addon/port-scanner/
2) For Google Chrome: https://chrome.google.com/webstore/detail/jicgaglejpnmiodpgjidiofpjmfmlgjo