How to Find Ports on Your Computer

Computer ports are virtual gateways that applications use to communicate over the network. Unlike the physical ports that peripherals to the computer, such as keyboards, mice, and USB drives, use, the ports in the discussion here exist entirely in the operating system. 

Your computer has thousands of these ports that applications rely on, typically to communicate over the internet with the webserver. Knowing the port number of an application allows you to open them. We’ll explain what exactly that means and more in our blog.

What is a Port?

As our brief introduction indicated, a port is a virtual aspect of an operating system that enables applications to communicate with web servers over the internet or other computers on a network. It is as essential for communication as an IP address. 

There are thousands of computer ports available on your operating system. The presence of ports allows network devices to distinguish the type of traffic flowing through and into the system. Each application or service uses a particular port to initiate a request to communicate externally. 

Ports use a standardized assignment. It means that regardless of whether you are running Windows or macOS, the type of application and its port usage will remain the same. For a quick example, web browser communication, which is HTTP and HTTPS traffic, uses port 80 and port 443, respectively. Similarly, SMTP, which is email traffic, uses port 25 by default. The assignment means that it is easy to distinguish what type of traffic is being handled by certain ports.  

How to Find a Port on Your Computer

The most common question, “how do I find my computer port” is technically inaccurate. There is not one port on your computer, and assignment varies. However, you can view what active ports are in use by your computer. 

A detailed list of active connections can be viewed easily by following this process: 

• Windows

1. Click on the Start button.
2. Type cmd and launch it. 
3. In the command interface, type netstat -aon and hit Enter.
4. Wait for a while. You will now have a list of all the ports being used by various applications on your computer. The PID column refers to the applications using the ports. You can look up the application by launching Resource Monitor by using the Windows search function. In the Resource Monitor window, locate an application using a PID. `

• macOS

1. Lookup Network Utility in the Spotlight search and launch it. 
2. Switch to the netstat tab in the utility window. 
3. Select a rule and confirm. 

TCP vs. UDP

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are two protocols that ensure the delivery of data packets. They belong to the Transport Layer (Layer 4) on the OSI model, just above Network Layer (Layer 3). 

While both of them deliver data, aspects such as reliability and connection state differ between them. TCP is more reliable in comparison because it establishes the handshake process and waits for an acknowledgment before sending the next data packet. It makes TCP suitable for sharing files. 

On the other hand, UDP is faster due to its “connectionless” status; it does not wait for an acknowledgment from the receiver. It makes UDP less reliable but faster for certain applications like video streaming and online gaming. 

Is a Port Different Than IP Address?

An IP address and a port are different aspects of network communication, but they work together. Circling back to the port lookup discussed earlier, the numbers next to your IP address are the port number. In an example, 445 is the port number in 192.168.0.1/445 used by the IP address. 

Where IP address defines a user or destination on a network, the port number acts as a gateway for the traffic. It is used so that multiple applications can communicate without collision. One IP address could have dozens of active connections through different ports. 

When Identifying Ports Matter

Ports are virtual gateways, and they work both ways. They support outbound traffic and inbound traffic, which means that any application or service on your computer can initiate a request to communicate with an external network or server. But due to security, that traffic will have a hard time reaching you because of the firewall between your computer and external networks. 

There are 65,535 TCP ports and 65,535 UDP ports available. Applications can be programmed to use from any of these ports. The Internet Assigned Numbers Authority (IANA) controls the distribution of IP addresses and port assignments to make them a standard. Services can register their preferred port number with the IANA. 

Port forwarding is a term that refers to allowing ports to accept external traffic and pass through the firewall and NAT without a hurdle. It is usually more important for online gaming as restrictions can affect gameplay performance and voice communication. 

Conclusion

Once you have figured out what ports are used by a program, you may want to open the ports.