There are different ways to classify ports according to their reference objects. If classified according to the nature of the port, it can usually be divided into the following three categories:
(1) Well-known ports: These ports are also commonly called "public ports". The port numbers of these ports range from 0 to 1024, and they are closely bound to some specific services. Usually, the communication of these ports clearly indicates the protocol of a service, and this port cannot be redefined. For example, port 80 is actually always used for HTTP communication, while port 23 is dedicated to Telnet service. These ports are usually not used by hackers like Trojans.
(2) Registered port: the port number ranges from 1025 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. Most of these ports have no clearly defined service objects, and different programs can define themselves according to actual needs.
(3) Dynamic and/or dedicated ports: the port number ranges from 49 152 to 65535.
According to different service modes, ports can be divided into "TCP protocol ports" and "UDP protocol ports". Because computers generally use these two communication protocols to communicate with each other. The "connection mode" mentioned above is a direct connection with the receiver. After sending the information, you can confirm whether the information has arrived. This mode mostly adopts TCP protocol. The other is not to connect directly with the receiver, but to send information on the Internet, regardless of whether the information arrives or not. This way mostly adopts UDP protocol, and IP protocol is also a connectionless way.
Two. Common network protocols
Internet layer protocols: including: IP protocol, ICMP protocol, ARP protocol, RARP protocol.
Transport layer protocols: TCP protocol, UDP protocol.
Application layer protocols: FTP, Telnet, SMTP, HTTP, RIP, NFS, DNS.
Common ports using TCP protocol mainly include the following:
(1)FTP: define the file transfer protocol, and use port 2 1. It is often said that when a computer starts FTP service, it starts file transfer service. FTP service is used to download files and upload home pages.
(2)Telnet: It is a remote login port, and users can connect to the computer remotely in their own capacity, through which they can provide a communication service based on DOS. For example, the previous BBS was a pure character interface, and the server supporting BBS opened port 23 to provide services to the outside world.
(3)SMTP: A simple mail transmission protocol is defined, and now many mail servers use it to send mail. For example, this mail service port is used in the commonly used free mail service, so it is often seen in the mail settings that there is such an SMTP port setting bar, and the server opens port 25.
(4)POP3: corresponding to SMTP, POP3 is used to receive mail. Generally, the POP3 protocol uses the port 1 10.
Commonly used UDP protocol ports are:
(1)HTTP: Hypertext Transfer Protocol. When surfing the internet, you have to open port 80 on the computer that provides web resources to provide services. It is often said that "WWW service" and "Web server" use this port.
(2)DNS: used for domain name resolution service, and most used in Windows NT system'. DNS uses port 53.
(3)SNMP: Simple network management protocol, which uses port 16 1 to manage network devices. In addition, proxy servers usually use the following ports:
(1). Common port number of HTTP protocol proxy server: 80/8080/3128/8081/9080.
(2).SOCKS proxy protocol server public port number: 1080.
(3) Commonly used port number of FTP protocol proxy server: 2 1.
(4).Telnet protocol proxy server universal port: 23
3. Computer port number query
netstat -a
4. How to add startup items to boot?
1, start/all programs/start, just put the shortcut on the icon of the program software you want to start.
2. Another method is to start/run, enter regedit to open the registry editor and expand it in turn.
[HKEY _ Local _ Machine Software Microsoft WindowsCurrentVersionRun]. Branch: Right-click the English or Chinese name of the program to be added to the new value in the right pane, then double-click it to add the exact path of the program in the numerical data, and press OK to restart (right-click the icon of the program to be added to select properties, and check "target" and "starting position" with the path and English name of the program software in the opened dialog box.
3. Start-Run-Enter msconfig and press Enter-Start-In the startup item, put a tick in front of the startup item (ctfmon.exe, input method) that you want to restore and remove, and press "Apply" and "OK".
4. Download some software (Windows optimizer, Jinshan cleaning expert, Super Rabbit).