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Telnet is one of the most widely used methods of sending and receiving passwords for local and remote logins. This article examined Telnet and its role in network authentication systems.

The main task of the Internet is to provide various services to users. For example, users want to run different programs on different sites and transfer the results to their personal computers. This requires using a client-server program, such as those that support the FTP and SMTP protocols. The best solution here is to create a general client-server application that allows users to access any application on their remote computer. Therefore, we need to use a program that allows users to log into their computers remotely. One of the most popular programs used in this field is Telnet, which can do this. Telnet is an abbreviation of two words, Terminal Network, which means “network terminal.”

Telnet is a two-way communication system that allows remote viewing of what is happening on a local computer.

Here we have two examples of login systems:

Local Login

When a user logs into a local computer, it is called “Local Login.” When a workstation activates a terminal, keystrokes (name and password or other authentication methods) are entered by the user and authenticated by the terminal driver. The terminal driver passes these characters to the operating system, which calls other software.

However, for operating systems, each character has a special meaning. For example, mixed characters can have a special meaning in the UNIX operating system. For example, combining Ctrl+Z keys in these operating systems means returning and canceling the activity. There should be no problem with the terminal driver in this situation, and it should work well with this character system. But in the login system, the use of combination keys can change the characters and cause problems in logging into the system.
Remote Login

This method is used when a user wants to log in to a host or local computer through a remote control program, so he must log in remotely (Remote Login).

How is remote login done?
On local sites

The user first enters his username and password in the terminal driver, after which these characters are sent to the Telnet client. Telnet client, in turn, converts these characters into universal characters that all network devices can understand. Here, the virtual network terminal checks the characters and then delivers them to the TCP/IP stack in the network. will be

at the remote site

The processing device translates Requests in NVT form into TCP/IP protocol. Here the characters are delivered to the operating system and then sent to the Telnet server. The Telnet server converts these characters so the remote computer can understand. However, the characters cannot be delivered directly to the operating system of the local or remote computer, and these computers cannot directly receive characters from the telnet server. Therefore, it is necessary to use software that can deliver these characters to the Telnet server. The operating system then receives these characters and delivers them to software and applications.

Network Virtual Terminal (NVT)

A virtual network terminal is a user interface that can specify the delivery of data and commands sent over a computer network.

In today’s world, systems are heterogeneous. For example, one operating system may precede a certain combination of characters as a file token termination, while another system interprets the same combination as a rollback. For example, in the DOS operating system, using Ctrl+z means going back to the previous step, while in the Unix operating system, you must use the combination keys Ctrl+D.

Telnet has solved this problem by defining a public user interface known as a Network Virtual Interface (NVT).

Telnet client-side software passes characters received from local terminals to the NVT, which is then delivered to the network. The Telnet server also takes the data received from the NVT and translates it into a language understandable by its remote computers.