What is TCP Port?

A TCP port is a virtual gateway that directs 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 the TCP ports and their use in Transmission Control Protocol (TCP). We have also listed different TCP port numbers and their functions.

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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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List of Common TCP Ports 

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

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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. 

How Do TCP and TCP Ports Work? 

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. 

How Do TCP Connections and Sockets Operate? 

A socket is an endpoint for communication between two systems running TCP server software. It combines an IP address and a TCP port number to create a unique communication channel.

This allows a single device to run multiple instances of the same service by assigning different TCP port numbers to each instance. For example, a web server may run "Site 1" on port 80 and "Site 2" on port 8080, allowing both websites to coexist on the same server. 

How to See Your Computer's 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. 

How do I find my TCP Port? 

To find your TCP port, 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. 

These methods help you identify active ports and connections on your system. 

Uses of TCP Ports 

● Ensure data reaches the correct application (e.g., port 80 for HTTP).

● Identify services with unique port numbers (e.g., port 3306 for MySQL).

● Route data packets to the right service.

● Enable secure remote communication (e.g., port 22 for SSH).

● Control traffic with firewalls.

● View active connections and open ports for diagnostics.

● Run multiple services on one device using different ports. 

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.