Port Numbers: A Comprehensive Guide
What are Port Numbers?
Port numbers are 16-bit unsigned integers ranging from 0 to 65535. They are used to identify specific applications or services on a computer network. When a client device connects to a server, the client sends the port number along with the server's IP address. The server then uses this port number to direct the client's request to the appropriate application or service.
Types of Port Numbers
There are three main types of port numbers:
Registered Ports
Port numbers from 1024 to 49151 are registered with the Internet Assigned Numbers Authority (IANA). These ports are used by well-known applications and services, such as HTTP (port 80), FTP (port 21), and SMTP (port 25).
Dynamic Ports
Port numbers from 49152 to 65535 are dynamic ports. These ports are assigned by the operating system on a temporary basis to applications that need to communicate over the network. Once the application closes, the dynamic port is released and can be reused by another application.
Private Ports
Port numbers from 0 to 1023 are private ports. These ports are not registered with IANA and are used for private communication between devices on the same network.
IANA's Role in Port Registration
IANA is responsible for coordinating the registration of port numbers for well-known applications and services. IANA maintains a list of registered port numbers that can be found on its website.
IANA's port registration process helps to ensure that there is no conflict between different applications and services using the same port number. This helps to maintain the stability and efficiency of the internet.
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