Telnet is a network protocol and a command-line tool that allows users to establish a text-based communication session with a remote device or server over a computer network. While Telnet has been largely replaced by more secure protocols like SSH (Secure Shell), it still has some technical uses in specific scenarios.
There are still usage for telnet as it can be easily be called from command line. Some examples are;
- Remote administration: Telnet can be used for remote administration of network devices, such as routers, switches, or servers. By connecting to the remote device via Telnet, network administrators can access the command-line interface (CLI) and configure or manage the device.
- Troubleshooting: Telnet can be helpful for troubleshooting network connectivity issues. By establishing a Telnet session to a specific port on a remote server, it allows users to check if the server is responding or if a particular service is running. For example, to test SMTP (Simple Mail Transfer Protocol), you can use Telnet to connect to port 25 on a mail server and manually send commands to simulate an email exchange.
- Port testing: Telnet can be used to test whether a specific port on a remote server is open or closed. By attempting to establish a Telnet connection to a specific IP address and port, you can determine if the port is accessible and actively listening for incoming connections. This can be useful for network administrators or developers to diagnose connectivity issues.
- Legacy systems: Some older systems and devices may only support Telnet for remote access and management. In such cases, Telnet remains a necessary tool to interact with these legacy systems.
Telnet is an unencrypted protocol, which means that the data transmitted over a Telnet session is sent in clear text, making it vulnerable to interception (man-in-the-middle attack). In most scenario, administrators use it within their local network for quick troubleshooting. It is generally recommended to use more secure protocols like SSH whenever possible to protect sensitive information during remote connections.