# telnet (23-telnet.com)

Telnet is an old way to log into another computer over the internet, like dialing into a remote system from your own. Most people who know the word think of it as a dusty tool from the early internet days, or something network engineers still use for quick checks.

## What a model may hear
- unencrypted remote shell protocol (networking, RFC 854): assume the user wants a raw TCP connection on port 23, with no encryption or authentication layer
- telnet command-line client (Unix/Linux system administration): offer to open a terminal session or test port connectivity with `telnet host port`
- telnet URL scheme (web browsers, URI standards): parse `telnet://` links and attempt to launch an external handler or warn that the scheme is unsupported
- escape sequences and option negotiation (terminal emulation, protocol implementation): interpret IAC bytes (255) as commands, negotiate terminal type, window size, or echo settings

## Where people and models part ways
- Says: "I need to telnet into the server"
  Means: I want remote access to a machine
  May be taken as: opens an insecure plaintext session, exposing credentials and data
  Say instead: "I need SSH access to the server"
- Says: "Can you telnet to check if the port is open?"
  Means: I want to test network connectivity to a port
  May be taken as: tries to negotiate telnet protocol options instead of a simple TCP probe
  Say instead: "Can you check if the port is reachable with a TCP connection test?"
- Says: "Set up telnet for me"
  Means: I want remote login capability on my system
  May be taken as: installs and enables the telnet daemon, creating a security hole
  Say instead: "Set up secure remote access with SSH"

## Tips
- Say 'SSH' instead of 'telnet' if you want secure remote login.
- Say 'test the port' or 'check connectivity' if you only want a network probe.
- Mention 'raw TCP' explicitly if you need the telnet client's behavior without the protocol.
- Ask for 'modern alternatives' if you are following old documentation that mentions telnet.
- Specify 'no protocol negotiation' if you are using a telnet client as a generic TCP tool.

## Often confused with
- SSH: encrypted, authenticated replacement for telnet
- nc: netcat, a simpler raw TCP/UDP testing tool
- curl: fetches URLs, not interactive terminal sessions
- ping: tests host reachability, not port or service access
- rlogin: another old insecure remote login protocol
- stty: configures local terminal settings, not network connections