The header of each TCP message contains a source port and a destination port, which are used to identify and distinguish the application processes of the source device and the destination device.
In the TCP/IP protocol stack, the source port number and the destination port number form a socket with the source IP address and the destination IP address respectively, which uniquely determines a TCP connection.
Compared with TCP message, UDP message has only a few fields: source port number, destination port number, length, checksum and so on. The function of each field is the same as that of the corresponding field in the TCP message.
Extended data:
According to the port number can be divided into three categories:
1, well-known ports: from 0 to 1023, which are closely bound to some services. Usually, the communication of these ports clearly indicates the protocol of a certain service. For example, port 80 has always been HTTP communication.
2. Registration port: from 1024 to 49 15 1. They are loosely bound to some services. In other words, many services are bound to these ports, and these ports are also used for many other purposes. For example, many systems handle a dynamic port of about 1024.
3. Dynamic and/or dedicated ports: from 49 152 to 65535. Theoretically, these ports should not be assigned to services. In fact, machines usually allocate dynamic ports from 1024. But there are exceptions: SUN's RPC port starts at 32768.
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