Main Application Layer Protocols

Common TCP ports include the following:

The telnet protocol is a member of the TCP/IP protocol family and is the standard protocol and main method of the Internet remote login service. It provides users with the ability to complete remote host work on local computers. Use the telnet program on the terminal user's computer to connect to the server. End users can enter commands in the telnet program. These commands will run on the server, just as they are directly entered on the server console. You can control the server locally. To start a telnet session, you must enter the user name and password to log on to the server. Telnet is a common method to remotely control web servers. It is a port used for remote login. You can remotely connect to a computer as your identity. This port can provide a communication service in DOS mode. For example, if the BBS is a character-only interface in the past, the BBS server can open port 23 to provide external services.

FTP: defines the file transfer protocol. Port 21 is used. It is often said that a certain computer has enabled the FTP service to start the file transfer service. You must use the FTP service to download files and upload them to the home page.

FTP is one of the TCP/IP protocol groups and is short for file transfer protocol. This Protocol is the basis for Internet file transfer. It consists of a series of specification documents to improve file sharing and provide non-direct use of remote computers, enables the storage medium to transmit data transparently and reliably and efficiently to users. Simply put, FTP is used to copy files between two computers. Copying files from a remote computer to a computer is called a "Download" file. If you copy a file from your computer to a remote computer, it is called an upload file. In TCP/IP protocol, the TCP port number of the FTP standard command is 21, and the port data port is 20.

SMTP (Simple Mail Transfer Protocol) is a Simple Mail Transfer Protocol. It is a set of rules used to send mail from the source address to the destination address, which controls the transfer mode of mail. The SMTP protocol belongs to the TCP/IP protocol family, which helps each computer locate the next destination when sending or transferring letters. The server specified by the SMTP protocol can send email to the recipient's server. The entire process takes several minutes. The SMTP server is a mail sending server that follows the SMTP protocol and is used to send or transmit emails. Use port: 25 during File Transfer

POP3The full name is "Post Office Protocol-Version 3", that is, "Post Office Protocol Version 3 ". Is a member of the TCP/IP protocol family, defined by rfc1939. This Protocol is mainly used to support remote management of emails on the server using the client. The POP3 protocol that provides SSL encryption is called pop3s.

POP3 default port: 110

POP3 default transmission protocol: TCP

Architecture applicable to POP3: C/S

POP3 protocol access mode: offline access

Commonly used UDP ports include:

DNS (Domain Name System) is a distributed database that maps domain names and IP addresses on the Internet, allowing users to access the Internet more conveniently, instead of remembering the number of IP address strings that can be directly read by machines. The process of obtaining the IP address corresponding to the host name through the host name is called domain name resolution (or host name resolution ). The DNS protocol runs on the UDP protocol and uses the port number 53.

HTTP: This is the most widely used protocol. It is often referred to as "Hypertext Transfer Protocol ". When browsing the Web page online, you have to open port 80 on the computer that provides web page resources to provide services. This port is often used for "WWW Service" and "Web server.

SNMP is a network management standard based on TCP/IP protocol families. Its predecessor is the simple gateway monitoring protocol (sgmp), which is used to manage communication lines. Subsequently, sgmp was greatly modified, especially when SMI and MIB compliant with Internet definitions were added: the improved protocol was the famous SNMP. The goal of SNMP is to manage software and hardware platforms produced by many manufacturers on the Internet. Therefore, SNMP is greatly affected by the internet standard network management framework. Now SNMP has been released to the third version, and its functions have been greatly enhanced and improved. Is based on UDP port 161

SOCKS: protocol for sessions traversal firewall SS firewall securely, it makes it easier and safer for client/server applications in TCP and UDP domains to use the services provided by the network firewall. In terms of concept, this protocol is a "shim-layer" between the application layer and the transport layer. Therefore, it does not provide network-Layer Gateway services such as passing ICMP information. Port 1080.