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What is a network port
2022-07-05 13:17:00 【Jinling shopkeeper】
As an operation and Maintenance Engineer , Even if it's not specialized in the Internet , I should have heard the concept of port , Then ask you a few small questions , See if you can answer ???
- What is a network port ?
- What is the port number ?
- Port number classification
- The role of the port number ?
- How to view the local port number
Windows
Linux
- IT The port number that personnel must know
In view of these problems mentioned above , Do a science popularization for friends who need to know . Everyone has Internet ports on their computers ( Mostly replaced by wireless modules )、USB Interface , These are actually ports , It is used for external connection , It is called hardware port here ; On the contrary, the network interface we usually mention is naturally the software port , Why software port ? Because it is originally used for “ Logical connection ”, Simply put, it is a port dedicated to the communication between programs , The communication links between programs are not visible to the naked eye , So it's logical connection . A port is the endpoint of a logical link , Therefore, a program will use the port when sending information . Ports are mainly used in the transport layer , to TCP 、UDP Agreement to use .
Port number Is a number assigned to the port , Range is from 0 To 65535. Always distinguish between them , It's like whether people have names .
port It can be divided into three categories , System ports 、 Register port and private port . System port (Well Known Ports): from 0 To 1023, They are tightly bound to some services . Usually, the communication of these ports clearly indicates a certain service The agreement of service . for example :80 Ports are actually always HTTP Communications ,443 Ports, etc . Registered port (Registered Ports): from 1024 To 49151. They are loosely bound to some services . That is to say, there are many services bound to these ports , These ports are also used for many other purposes . for example : Many systems handle dynamic ports from 1024 Start around , for example mysql Of 3306 port . Dynamic and / Or private port (Dynamic and/or Private Ports): from 49152 To 65535. Theoretically , These ports should not be assigned to services . actually , Machines usually come from 1024 Start allocating dynamic ports . But there are exceptions :SUN Of RPC Port from 32768 Start
The role of the port number It is used for communication between programs , The service functions of each network are different , Therefore, it is necessary to send different packets to different services for processing , When your host is turned on at the same time FTP And WWW The service , Data packets sent by others , According to TCP above port Give me the number FTP This service or WWW This service deals with . A simple example , Tom's house has 5 A door , Entering from different doors can have different results , For instance from 1 Enter through the door , You can sleep in the master bedroom , from 2 Enter through the door , You can enter the kitchen to cook , from 3 You can go to the bathroom when you enter through the door …… The door here can be understood as a port , Entering from different doors and doing different things is similar to what we call programs or services with different functions . As for this house, it is equivalent to IP Address , Therefore, we can also see a IP An address can have multiple port numbers . Like your computer IP The address is 192.168.1.3, But the various services on your computer have many port numbers .
View port number have access to netstat command , The following figure shows that windows and linux How to view the port number .
windows
LINUX
Common port number
20: File transfer protocol (FTP) The data transfer
21: File transfer protocol (FTP) Command control
22:SSH
23:Telnet
25:SMTP, Simple mail transfer protocol
53:DNS
80:HTTP
123:NTP, Network time protocol
161:SNMP, Simple network management protocol
443:HTTPS
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