Use telnet as a quick raw TCP probe to verify service reachability and exchange minimal protocol data. 16.11.2025 | reading time: 3 min Telnet is a tiny tool with big diagnostic value: it opens a raw TCP connection so he can check whether a service is reachable and even speak the protocol by hand, without any special client libraries or GUI. Quick hands-on: HTTP check Start a raw TCP session to port 80 and send a minimal HTTP request to prove reachability and see the server response: ``` $ telnet example.com 80 Trying 93.184.216.34... Connected to example.com. Escape character is '^]'. GET / HTTP/1.0 Host: example.com HTTP/1.0 200 OK Content-Type: text/html; charset=utf-8 <html>...</html> Connection closed by foreign host. ``` Another real case: SMTP test To verify a mail server reachability and basic SMTP dialogue, connect to port 25, wait for the banner and type protocol commands by hand; for example after `telnet mail.example.local 25` you might see a 220 banner and then type `HELO host.example.local` to check replies; press Ctrl+] to get the telnet prompt and then type `quit` to exit. What to watch and how to use it Telnet speaks raw TCP and nothing more, so it will not do TLS or authentication; use it to confirm routing, firewall rules and service listeners, to inspect simple text protocols by hand and to reproduce client behavior; remember it is unencrypted and often blocked, and many distributions do not install a telnet client by default so the package is usually named "telnet" in your distro repository. Tools that complement telnet When you need port scanning, banner grabbing or encrypted connections, combine telnet with other utilities: `nc` or netcat for scripted TCP I/O, `nmap` for discovery and service detection, and `openssl s_client` for TLS checks; each fills gaps telnet leaves open. Telnet is simple, blunt and very useful for quick checks; learn to use it alongside more modern tools and he will gain reliable, repeatable troubleshooting skills that scale; consider deepening Linux knowledge and pursuing certifications such as CompTIA Linux+ or LPIC-1 with intensive exam preparation at bitsandbytes.academy. Join Bits & Bytes Academy First class LINUX exam preparation. network utilities troubleshooting
