portszámok

A portszámok, vagyis port numbers, are used in computer networking to identify specific applications or processes running on a network device. They are part of the Transport Layer of the TCP/IP model, specifically used with protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). When data arrives at a computer, the port number tells the operating system which application should receive that data. Think of an IP address as the street address of a building and a port number as the apartment number within that building.

Port numbers range from 0 to 65535. These are divided into three categories. Well-known ports, from 0 to 1023, are reserved for common services and applications. For example, port 80 is used for HTTP (web browsing), port 443 for HTTPS (secure web browsing), and port 25 for SMTP (email sending). Registered ports, from 1024 to 49151, can be registered by software vendors for specific applications, though this is less common. Dynamic or private ports, from 49152 to 65535, are typically used for temporary or ephemeral connections.

When a client application initiates a connection to a server application, it uses the server's IP address and the server application's well-known or registered port number. The client application will also use a dynamically assigned port number for its outgoing communication. This allows for multiple connections to the same server on the same IP address simultaneously, each directed to a different service or application.