Understanding of Telnet

The Telnet protocol is a member of the TCP/IP protocol family and is the standard protocol and main way of Internet remote Login service. It provides users with the ability to perform remote host work on the local computer. Use the Telnet program on the end user's computer to connect to the server. End users can enter commands in the Telnet program that run on the server as if they were entered directly on the server's console. The server can be controlled locally. To start a Telnet session, you must enter a user name and password to log on to the server. Telnet is a common way to remotely control a Web server.

Telnet can be used as a communication protocol, but for intruders, Telnet is only a remote login tool. Once the intruder establishes a Telnet connection with the remote host, the intruder can use the hardware and software resources on the target host, and the intruder's local machine is only the equivalent of a keyboard and display terminal.

Why do I need Telnet?

1. Telnet is to see if a port is accessible. When we are doing development, the port we often use is 8080. Then you can start the server and use Telnet to see if the port is available.

2. telnet command for remote login, the Internet Early BBS Forum is the use of Telnet login. The telnet command uses the detailed telnet command to log on as follows: Telnet hostname/IP initiates a telnet session. Example: Telnet 192.168.0.1 If this command succeeds, it will get the login: Prompt from the remote machine. Once Telnet is successfully connected to the remote system, the login information is displayed and the user is prompted to lose the user name and password. If the user name and password are entered correctly, they will be able to log on successfully and work on the remote system. You can enter many commands after the Telnet prompt to control the Telnet session, which is described in detail in the Telnet online Help manual. After the user finishes the remote session, be sure to use the logout command to exit the remote system. Then Telnet reports that the remote session was shut down and returned to the user's local machine at the shell prompt. R-Series commands in addition to FTP and Telnet, you can use the R-series commands to access remote computers and Exchange files on the network. Using the R-Series commands requires special attention, because if the user is not careful, it can cause a serious security breach. After the user issues an R-series command, the remote system checks the file named/etc/hosts.equiv to see if the user's host is listed in the file. If it does not find the user's host, check the remote machine with the same name as the user's home directory named. Rhosts file to see if the host of the user is included. If the user's host is included in any of these two files, the user does not have to provide a password to execute the R-series command. Although it may be convenient for users to not have to type a password every time they visit a remote machine, it can also pose a serious security issue. We recommend that users carefully consider the security implications of the R-command before establishing the/ETC/HOSTS.EQUIV and. rhosts files.

When Telnet logs in to a remote computer system, it actually starts two programs: one is a telnet client, runs on a local host, and the other is a Telnet server program that runs on the remote computer that you are logging on to.

Telnet protocol:

Telnet is a protocol located at layer 7th of the OSI model---application layer, a TCP/IP protocol that provides connectivity to remote host terminal emulation by creating a virtual terminal. This protocol needs to be authenticated by username and password and is the standard protocol for Internet remote Login service. The application of the Telnet protocol can turn the computer used by the local user into a terminal of the remote host system. It provides three basic services:

1) Telnet defines a network virtual terminal to provide a standard interface for a remote system. The client program does not need to know more about remote systems, they only need to construct programs that use standard interfaces; 2) Telnet includes a mechanism to allow client and server negotiation options, and it also provides a set of standard options; 3) Telnet symmetrically handles both ends of the connection, That is, Telnet does not force the client to enter from the keyboard, nor does it force the client to display output on the screen. What's the use of Telnet? Telnet provides remote login capability so that users can log on to the remote Telnet server by running the Telnet client on the local host. Commands that are entered locally can be run on the server, and the server returns the results locally as if it were operating directly on the server console. This allows remote operation and control of the server locally.

Understanding of Telnet