Computers and devices connect to each other through physical connections – these are the hardware ports such as Ethernet port. They also connect to each other through wireless ports. Now “computers” could mean phones, devices, sensors or anything that needs to talk to other devices/computers. These ports enable the computers to talk to each other easily. The computers talk to each other by assigning address to physical computers. These addresses are many and with the IPv4 convention, it allowed 4 Billion addresses. However, with the new convention IPv6, expanded it to 340 undecillion permitting many more devices.
A port, in the “incoming” context though usually refers to a logical port which is a number from 0 to 65535 that the operating system uses to route the incoming connection. This becomes the destination port for the other computer that is reaching into – or talking to – this incoming computer. Now this is useful because one computer now can host a variety of services dependent on the port. For example, port 80 is used for http – the internet web connections that we use on the browser everyday and port 443 is used for HTTPS – the secured way for the same internet web connections. Other standard ports are 22 for a secure shell, custom web apps go to port 8080.
Now when one computer talks to the other for a specific service, then you can create custom ports. For example – port 3001. When the receiving computer is listening on port 3001 to serve a specific application, the requester must also send a request on that specific port – 3001. That way both the computers know what to expect.
Ports for websites are so standard in browsers that they do not need to be specified, but in other contexts, they do need to specified and are usually written followed by a “:” colon. So for internet address 10.100.1.3 the port 198 will be specified by 10.100.1.3:198.
Port specification make almost all applications and API’s work on the internet.
