https://www.devkuma.com/en/tags/telnet/ https://www.devkuma.com/en/tags/telnet/logo/180x180.jpg https://www.devkuma.com/en/tags/telnet/ Recent content in Telnet on devkuma Hugo -- gohugo.io en kc@example.com (kc kim) kc@example.com (kc kim) The devkuma https://www.devkuma.com/en/docs/telnet/ Sun, 03 Apr 2022 18:02:00 +0900 kc@example.com (kc kim) https://www.devkuma.com/en/docs/telnet/ <h2 id="telnet">Telnet</h2> <p>The Telnet service on the Internet is a service that lets you connect to another computer, especially one using the UNIX operating system, and use it as if a keyboard and monitor were connected directly to that computer.</p> <ul> <li>It is an Internet standard protocol supported when connecting to a remote host computer through the Internet.</li> <li>It is a TCP/IP-based protocol.</li> <li>It is a remote terminal connection service.</li> <li>TCP port number 23 is used by default.</li> </ul> <p>It can display only a text screen rather than a graphical screen, but it is still widely used because it is simple, fast, and allows direct use of UNIX. However, to use Telnet well, you need to learn UNIX commands, and because only a text screen can be used, it is difficult to use without special knowledge.</p> <h2 id="telnet-characteristics">Telnet Characteristics</h2> <ul> <li>Telnet is a kind of terminal emulation protocol and uses the concept of a virtual terminal called NVT (Network Virtual Terminal).</li> <li>It has a one-to-one symmetric relationship between the terminal and the host.</li> <li>Additional option negotiation is possible.</li> </ul> <h3 id="what-is-nvt-network-virtual-terminal">What Is NVT (Network Virtual Terminal)?</h3> <ul> <li>NVT is the most basic part of the Telnet protocol. When the remote system to connect to and the local system have different versions and therefore different data formats, it is a virtual device that converts data for smooth communication.</li> <li>NVT defines basic terminal control characters.</li> </ul> <p><img src="https://www.devkuma.com/docs/internet/telnet_nvt.jpeg" alt="NVT(Network Virtual Terminal)"></p> <h2 id="how-telnet-works">How Telnet Works</h2> <p><img src="https://www.devkuma.com/docs/internet/telnet_flow.jpeg" alt="How Telnet works"></p> <ol> <li>The client establishes a TCP connection to the remote system (server) through remote login. (Default port 23)</li> <li>The remote system provides a virtual terminal to the connected client.</li> <li>The client executes commands on the remote system as if it were an actual terminal.</li> <li>The remote system executes the client&rsquo;s command and sends the result back to the client.</li> </ol> <h2 id="telnet-connection-clients">Telnet Connection Clients</h2> <ul> <li>Server and client built into Windows by default <ul> <li>For security reasons, the feature is disabled by default. To use it, it must be enabled in settings.</li> </ul> </li> <li>Putty, SecureCRT, Xshell, and similar tools can be used conveniently.</li> </ul> <h2 id="references">References</h2> <ul> <li><a href="http://egloos.zum.com/guswl47/v/6481497" target="_blank" rel="noopener">Telnet protocol analysis and packet analysis (1)<i class="fas fa-external-link-alt"></i></a></li> </ul> Network Internet Telnet