1, Telnet protocol allows users on one machine to log on to a remote machine to work;
2.FTP protocol provides a method to transfer files from one machine to another;
3.SMTP protocol is used to send and receive e-mail;
4.HTTP protocol is used to obtain the homepage on WWW.
(Note: DNS protocol uses both TCP53 port and UDP53 port. DNS protocol provides domain name resolution service at UDP53 port and DNS regional file transfer service at TCP53 port. )
Extended data:
1, Telnet (telecommunications network).
Telnet protocol is a member of TCP/IP protocol family, and it is the standard protocol and main mode of Internet remote login service. It provides users with the ability to log on to a remote host on the local computer. Connect to the server using the telnet program on the end user's computer. Which is used for realizing the remote login function.
End users can enter commands in the telnet program, and these commands will run on the server as if they were entered directly on the console of the server. You can control the server locally. To start a telnet session, you must enter a user name and password to log in to the server.
2. File transfer protocol
Based on the client server model, FTP protocol includes two parts, one is FTP server and the other is FTP client. FTP protocol provides interactive access, connection-oriented, and uses TCP/IP to provide more reliable transmission services. Main function: reduce/eliminate the incompatibility of files under different operating systems.
In the process of FTP interaction, the client tells the server relevant information through command words. Commonly used access control commands include user, access, CWD, exit, etc. There are five transmission parameter commands: port, PASV, type, STRU and mode; There are twenty FTP service commands, such as RETR, STOR, List and ABOR. ?
3.SMTP (Simple Mail Transfer Protocol)
Basic functions: writing letters, transmitting reports, transmitting reports, displaying letters, and processing letters by the receiver.
SMTP is a protocol that provides reliable and efficient e-mail transmission. SMTP is a mail service that imitates FTP file transfer service. The SMTP server listens for customer requests on the default port 25, which is mainly used to transmit mail information between systems. Is a connection-oriented client/server model.
4.DNS protocol (domain name service)?
The IP address composed of numbers is difficult to remember, so we use the alias of the IP address of the website-domain name. In fact, domain names correspond to IP addresses, and this correspondence is stored in DNS servers.
After entering the domain name in the browser, the DNS server will resolve the domain name into the corresponding IP address. Note that this is different from the ARP protocol of the network layer: DNS provides the correspondence between domain names and IP addresses, while ARP provides the correspondence between IP addresses and MAC addresses.
5.HTTP (Hypertext Transfer Protocol).
It is reliable transmission based on TCP and adopts client/server working mode. The browser sends a request to the server, and the server responds to the corresponding web page, which is a transmission protocol for transmitting hypertext from the World Wide Web server to the local browser.
In the process of HTTP communication, firstly, the client sends a request to the server to establish a link, which is completed through TCP three-way handshake, and then the client sends a request to the server to tell the server what it wants. The server returns the information needed by the client through the response. Finally, the link is closed by TCP four-time handshake, thus completing a basic communication process.
References:
TCP/IP Protocol-Baidu Encyclopedia