TCP port represents an application or service-specific endpoint identifier. It is represented as a 16-bit number (approx. 65,536 port numbers).
IP address identifies the device in the network, whereas ports specifies which application or service on a device should receive the incoming data.
Why TCP port
Identify applications
Each port number is associated with a specific application or service running on a computer. It serves as an identifier that allows incoming network data to be directed to the appropriate application or service.
Listen for connections
Ports are used to indicate that an application is actively listening for incoming network connections on a particular port number. When a connection request is made to that port, the application is alerted to establish a connection with the remote device.
Reserved ports
Many ports are reserved for specific protocols and services. Theses ports are standardised, ensuring that specific services are associated with specific port numbers across different systems.
- Port numbers 0 - 1023: are used for well-know ports
In particular, the web protocol HTTP has port 80 reserved, and the email protocol
SMPT has port 25 reserved. - Port numbers 1024 - 65535: are available for the following user application
- Port number 1024 - 49151: (Registered ports) reserved for user server applications
- Port number 49152 - 65535: (Dynamic/Private ports) reserved for clients for custom use or temporary purposes.
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