Virtual port number in socket port

Port number

Protocol Port number:

The full name of the port number is the protocol port number, it is used for the application layer and transfer into the interaction, when creating a socket need to know the IP address and port number, here the port number is virtual, Transport layer protocol We know that the port number is a 16-bit integer, then represents 0 to 65535 so many port numbers, What is the use of him?

If the IP is to determine the network is the only one host, then the IP port number is the only one in the network to determine the only one of the process, note that the port number refers to the local meaning, he only in order to mark the application layer of the various processes and transport layer interaction in the layer of the indirect port, There is no correlation between the port numbers of different computers in the Internet.

The majority of the known port numbers are preserved in the Etc/services file.

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Classification of protocol port numbers:

1> The port number used by the server side: Here is divided into two categories, the most important class is known as the port number or the system port number, the value is 0~1023, these values can be found in the URL www.iana.org. The IANA assigns these port numbers to some of the most important applications in TCP/IP, which are known to all users. When a new application appears, the IANA must assign him a well-known port, or else the application process on the Internet will not be able to communicate with him. Another class is called the registration port number , which is used for applications that do not have a well-known port number, and the use of such port numbers must be in the IANA to prevent duplication in accordance with the prescribed level of formality.

2> The port number used by the client: The value is 49152~65535, because this type of port number is dynamically selected when the client process is running, so called the ephemeral port number is left to the client process to choose to use temporarily. When the server process receives a message from the client process, it knows the port number used by the client process, so it can send the data in the past and the port number used after the end of the communication ceases to exist.

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Virtual port number in socket port