telnet
Networking
Usage
telnet <host> <port>Opens a plain TCP session in which everything travels in clear text, so it must never be used to log in (that is ssh); its remaining use is checking whether a port answers, and you leave with Ctrl+] then quit.
Common flags
| Flag | Meaning |
|---|---|
| <host> <port> | Open a raw TCP connection and type into it. |
| Ctrl+] then quit | How to get out when the far end never closes. |
| -4 / -6 | Force one address family. |
| -e <char> | Choose a different escape character. |
Examples
telnet example.com 80Then type: GET / HTTP/1.0 and press enter twice.
telnet 192.168.1.1 22Read the SSH banner to confirm the service answers.
When a connection fails, these narrow down how far it got — name not resolving, no route, or a blocked port.
How to read this
- Square brackets [ ] mark a part you may leave out.
- An ellipsis … means you can list more than one.
- Flags are case-sensitive — in some commands -r and -R do different things.
Questions
Q. What does telnet do?
Opens a plain TCP session in which everything travels in clear text, so it must never be used to log in (that is ssh); its remaining use is checking whether a port answers, and you leave with Ctrl+] then quit.
Q. How do I type it?
telnet <host> <port> — square brackets mark the parts you can leave out.
Q. How many flags are worth knowing?
4 are listed here; the full set is in man telnet. This command sits under Networking.
Related commands
man page: man telnet