When surfing the Internet, we often see the word "port" and often use the port number. For example, the "21" added after the FTP address, 21 represents the port number. So what does the port mean? How to check the port number? The following will introduce this content.
Port concept
existnetworkIn technology, ports (Ports) have roughly two meanings: one is a port in the physical sense, for example,ADSLModem, hub, switch, router are used to connect to other network devices, such as RJ-45 port, SC port, etc. The second is a port in the logical sense, which generally refers to the port in the TCP/IP protocol. The port number ranges from 0 to 65535, such as port 80 for browsing web services, port 21 for FTP services, etc. What we are going to introduce here is ports in the logical sense.
Port classification
There are many classification standards for ports in the logical sense. The following will introduce two common classifications:
1. Distribution by port number
(1) Well-Known Ports
Well-known ports are well-known port numbers, ranging from 0 to 1023, and these port numbers are generally fixedly assigned to some services. For example, port 21 is allocated to the FTP service, port 25 is allocated to the SMTP (Simple Mail Transfer Protocol) service, port 80 is allocated to the HTTP service, port 135 is allocated to the RPC (Remote Procedure Call) service, etc.
(2) Dynamic Ports
Dynamic ports range from 1024 to 65535. These port numbers are generally not fixedly assigned to a certain service, which means that many services can use these ports. As long as the running program requests to the system to access the network, the system can assign one of these port numbers for use by the program. For example, port 1024 is assigned to the first procedure to issue an application to the system. After closing the program process, the occupied port number will be released.
However, dynamic ports are often used by virus * programs, such as the default connection port of Glacier is 7626, WAY 2.4 is 8011, Netspy 3.0 is 7306, YAI virus is 1024, etc.
2. Divided by agreement type
According to the protocol type, it can be divided into TCP, UDP, IP and ICMP (Internet Control Message Protocol) and other ports. The following mainly introduces TCP and UDP ports:
(1) TCP port
The TCP port, that is, the transmission control protocol port, requires a connection between the client and the server, which can provide reliable data transmission. Common ones include port 21 of the FTP service, port 23 of the Telnet service, port 25 of the SMTP service, port 80 of the HTTP service, etc.
(2) UDP port
UDP port, that is, the user packet protocol port, does not require a connection between the client and the server, and its security is not guaranteed. Common ones include port 53 for DNS service, port 161 for SNMP (simple network management protocol) service, port 8000 and 4000 for QQ, etc.
Port concept
existnetworkIn technology, ports (Ports) have roughly two meanings: one is a port in the physical sense, for example,ADSLModem, hub, switch, router are used to connect to other network devices, such as RJ-45 port, SC port, etc. The second is a port in the logical sense, which generally refers to the port in the TCP/IP protocol. The port number ranges from 0 to 65535, such as port 80 for browsing web services, port 21 for FTP services, etc. What we are going to introduce here is ports in the logical sense.
Port classification
There are many classification standards for ports in the logical sense. The following will introduce two common classifications:
1. Distribution by port number
(1) Well-Known Ports
Well-known ports are well-known port numbers, ranging from 0 to 1023, and these port numbers are generally fixedly assigned to some services. For example, port 21 is allocated to the FTP service, port 25 is allocated to the SMTP (Simple Mail Transfer Protocol) service, port 80 is allocated to the HTTP service, port 135 is allocated to the RPC (Remote Procedure Call) service, etc.
(2) Dynamic Ports
Dynamic ports range from 1024 to 65535. These port numbers are generally not fixedly assigned to a certain service, which means that many services can use these ports. As long as the running program requests to the system to access the network, the system can assign one of these port numbers for use by the program. For example, port 1024 is assigned to the first procedure to issue an application to the system. After closing the program process, the occupied port number will be released.
However, dynamic ports are often used by virus * programs, such as the default connection port of Glacier is 7626, WAY 2.4 is 8011, Netspy 3.0 is 7306, YAI virus is 1024, etc.
2. Divided by agreement type
According to the protocol type, it can be divided into TCP, UDP, IP and ICMP (Internet Control Message Protocol) and other ports. The following mainly introduces TCP and UDP ports:
(1) TCP port
The TCP port, that is, the transmission control protocol port, requires a connection between the client and the server, which can provide reliable data transmission. Common ones include port 21 of the FTP service, port 23 of the Telnet service, port 25 of the SMTP service, port 80 of the HTTP service, etc.
(2) UDP port
UDP port, that is, the user packet protocol port, does not require a connection between the client and the server, and its security is not guaranteed. Common ones include port 53 for DNS service, port 161 for SNMP (simple network management protocol) service, port 8000 and 4000 for QQ, etc.