Shulou(Shulou.com)06/03 Report--

Today, what I want to share with you is what linux port means. I believe many people don't know much about it. In order to let you know more about linux port, I summarized the following contents for you. Let's look down together. I'm sure you'll get something.

Services provide functions to the system. In the system, there are not only system services, but also network services. Each network service has its own port, and the general port number is fixed. So, what is a port?

We know that the IP address is the address number of the computer on the Internet, and each networked computer must have its own IP address and must be unique in order to communicate normally. In other words, the location of different computers is determined by IP addresses on the Internet.

You can think of the IP address as the "house number" of the family. Whether you live in a courtyard, an apartment building or a villa, you have your own house number, and the house number is unique.

If we know the IP address of a server, we can find the server. But there may be many network services built on this server, such as WWW service, FTP service, Mail service, so which network service do we need the server to provide for us? At this point, it is up to the Port to tell the difference, because the port corresponding to each network service is fixed.

For example, the port corresponding to the WWW service is 80, the port for the FTP service is 20, and the port for the 21 gravity mail service is 25 and 110. In other words, the IP address can be thought of as a "house number", while the port can be thought of as a "family member". If you find the IP address, you can only find your home. Only when you find the port, can you find the real recipient when you send the letter.

In order to unify the corresponding relationship between the ports of the entire Internet and network services, so that all hosts can use the same mechanism to request or provide services, the same service uses the same port, this is the protocol.

Protocols in computers fall into two main categories:

Connection-oriented reliable TCP protocol (Transmission Control Protocol, transmission control protocol)

Connectionless and unreliable UDP protocol (User Datagram Protocol, user Datagram protocol)

Both protocols support 216, or 65535 ports. How do you remember so many ports? The system provides us with the corresponding file / etc/services of the service and the port. View-below:

[root@localhost] # vi / etc/services... Omit part of the output. Ftp-data 20/tcpftp-data 20/udp# 21 is registered to ftp, port for but also used by fspftp 21/tcpftp 21/udpfsp fspd#FTP service … Omit part of the output. The port on which smtp 25/tcp mailsmtp 25/udp mail# mail sends letters. Omit part of the output. Port of http 80/tcp www www-http # WorldWideWeb HTTPhttp 80/udp www www-http # HyperText Transfer Protocol#WWW service … Omit part of the output. The port on which pop3 110/tcp pop-3# POP version 3pop3 110/udp pop-3# mail receives mail. Omit part of the output.

Can the port of the network service be modified? Of course, but once the port is modified, it will be difficult for the client to know what the server port is when accessing the server, and will not be able to get the service correctly. Therefore, do not modify the corresponding port of the network service except in the experimental environment.

About what the meaning of linux port is shared here, I hope that the above content can have a certain reference value for everyone, you can learn to apply. If you like this article, you might as well share it for more people to see.

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