What’s a Network Port?

A big part of how computers communicate is through network ports.

There's probably several things that we want to do for our business, techknowdj.com. For one, we want a website, so we're going to set up a service that's going to deliver a website. Also, we want to have that list of songs to be able to communicate to our app so that the app can go and request a list of songs. Also, the streaming of music looks very different, so we probably are going to have a different program that's going to be set up for streaming music.

So we have a lot of different types of requests that are coming into the server. For instance, one for our web page. We have one from our app that's trying to connect to our server. We also probably set up a separate service for streaming, because that streaming traffic looks very different from these other types of traffic that we have over here. There are other types of connections that we might have set up too, like remoting into this server, which would be a different type of connection.

So there's a lot of different services that this server could be offering. How does it keep track of these different requests and what service they're requesting it from? That's where ports come into play. Ports allow traffic that's coming into the server to be able to know what service it's going to be sent to.

For instance, with our web traffic, that's commonly assigned to port 80 or 443 — 443 for secured traffic, port 80 for insecure traffic. And so everything actually is going to 443. But when a user makes a connection requesting port 80, it's going to be sent to that web service and respond to that. Or maybe the app that we're creating, perhaps we assign port 81 to it. Maybe that streaming service, we assign port 82 to it. So each one of these services is going to be assigned a port, so that way when traffic comes into this server, it understands what service it's associated with.

Port number groups

There are port ranges here, so let's talk about port number groups. A range from 0 to 1,023 is what we call the well-known ports. These ports are the ones that are really already spoken for, so we typically don't use those for other services that we would create. It would just be for the services that are already created, like web traffic.

And then there's these registered ports, the 1,00 to 49,000 range right here. Those are supposed to be ones that you actually register, so if you're going to use it, you should register it. Although a lot of times we will use ports in that range and not register it. And then there's these dynamic, private or ephemeral ports. We won't get into the details of all of these port assignments; just know that there's these certain ranges.

Here are some of those well-known ports and the services that are associated with those ports. Once again, we mentioned port 80 is associated with HTTP traffic — that's that web traffic — and 443, which is the secure method of HTTP. So those would be associated with those web services. And so when traffic comes in to port 80 or 443, it's usually for web pages and websites.