Common TCP Ports and Their Applications

TCP ports are virtual gateways that direct data to specific services or applications using assigned port numbers. TCP ports ensure reliable communication for tasks like web browsing, email, or file transfers.

In this article, we have explained what a TCP port is and listed different TCP ports and their functioning in the Transmission Control Protocol. Furthermore, if you are interested in learning more about such Internet Protocols, you can check out our online IT infrastructure courses.

What is a TCP Port?

A TCP port is a logical endpoint in computer networking that allows data to flow between different applications or services. Each TCP port is associated with a unique service or application, ensuring the reliable delivery of data packets.

When data is sent over a network, the TCP protocol uses the combination of an IP address and a port number to ensure the data reaches the correct application or service. The TCP port number allows different services to operate on the same device, each listening on a specific port for incoming data.

Did you know? There are 65,535 available TCP Ports.

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Why are TCP Ports Needed?

When devices communicate via TCP, they rely on TCP ports to determine the service/application being used. For example, when you enter a website address, your browser connects to the server’s IP address on a specific TCP port ( typically port 80 for HTTP or port 443 for HTTPS).

These TCP ports enable devices to send data to the correct service or application, ensuring smooth communication between the source and destination.

Types of TCP Ports

There are three types of TCP Ports:

1. Well-known Ports (0–1023): Reserved for standard services like HTTP (port 80), FTP (port 21), and SSH (port 22).

2. Registered Ports (1024–49151): Assigned to user-defined services and applications that are not universally known but still require unique ports.

3. Dynamic or Private Ports (49152–65535): Typically used for temporary, ephemeral connections.

List of Common TCP Ports and Applications

Below is a table of commonly used TCP port numbers, their corresponding protocols, and typical use cases:

How TCP Ports Power Your Daily Online Activities

Every time you browse a website, send an email, or connect to a remote server, TCP ports are quietly working behind the scenes to make it happen.

Here are some examples showing how you use TCP ports in your everyday lives.

● TCP ports allow browsers to communicate with web servers, ensuring that web pages load correctly. For instance, port 80 handles standard HTTP traffic, while port 443 is used for secure HTTPS connections.

● System administrators use TCP ports to securely access servers from remote locations. Port 22 is commonly used for SSH (Secure Shell), which provides encrypted command-line access and file transfers.

● Email clients and servers rely on specific TCP ports to send and receive messages. Port 25 is used for SMTP to send emails, while ports 110 and 143 are used for POP3 and IMAP, respectively, to retrieve emails.

● Firewalls use TCP port numbers to control network traffic, allowing or blocking access to specific services. For example, blocking port 23 can prevent insecure Telnet access, while allowing port 443 enables secure web browsing.

● TCP ports facilitate file sharing between devices, especially in enterprise environments. FTP (File Transfer Protocol) uses ports 20 and 21 to upload and download files.

Security Risks with TCP Ports

TCP ports, while essential for internet communication, can also be exploited if not properly secured. Open or misconfigured ports may expose systems to unauthorized access, data breaches, and malware attacks.

For example, leaving port 23 (Telnet) open can allow attackers to gain remote access using unencrypted credentials. Similarly, ports used by outdated or vulnerable services like port 445 for SMB can be targeted by worms and ransomware.

Attackers often scan for open ports to identify potential entry points, making it crucial to monitor and restrict access using firewalls, intrusion detection systems, and regular port audits.

How to Find Active TCP Ports on your Computer?

To find active TCP ports on your computer, follow these methods based on your operating system:

1. Using Command Prompt (Windows):

Open Command Prompt (type cmd in Start menu), then type "netstat -an" to display active connections and port numbers. To filter for a specific port, use " netstat -an | find "8080".

2. Using Terminal (Mac/Linux):

Open Terminal and type " netstat -an | grep LISTEN " to list all open TCP ports.

3. Using Terminal Linux

In Terminal, type "sudo lsof -iTCP -sTCP:LISTEN -P" to see open TCP ports and associated processes.

How to Check TCP Connections?

To view TCP connections on your machine, you can use the netstat command-line tool, regardless of your operating system. The specific syntax may vary depending on your OS.

On Windows, you can open the command prompt and enter " netstat -a " to display a list of all active TCP connections on your system.

Alternatively, you can use the command " netstat /? "to get more detailed information, including a comprehensive list of parameters and options, making it more useful for analyzing network connections.

TCP Ports vs UDP Ports

TCP and UDP are foundational protocols in the TCP/IP suite, each designed to handle different types of network communication.

While they both use port numbers to identify specific services, the way they operate and manage data transmission is quite different.

The table below highlights the key differences between TCP and UDP ports, helping you understand how each protocol supports various internet functions.

Conclusion

In summary, TCP ports are integral to communication in a TCP/IP network. They provide the structure for identifying services and applications on a device, enabling smooth data transfer between systems.

With the vast number of available TCP ports and their classifications, network communication can remain organized and efficient, ensuring reliable service delivery across devices.