Testing the status of the computer port on a subnet is only possible with openport activation. Besides, remember that if you have an open port for your local IP address. That is if you're not sure about the IP address and port, you can find out more about Ports forwarding/activation on google. What is the port forwarding? Port forwarding is a special router configuration that can be used to forward external requests from the Internet space to computers or other devices on the local network. You can determine which local computer sends data and connection requests that end up at a specific port on the router.
The purpose of ports checker; Send a virtual address to a computer or network device that allows communication with other the computer or other devices. If an application or service decides to engage with the network, it opens a port with a unique number through which it can work with remote servers. In a layman term, it would read: "I, the server program, open port 1234. If the network cable comes with the data number 1234 - that's you."