Editing Telnet (section)

=== Modern day uses ===
The Telnet protocol is mainly used for legacy equipment that does not support more modern communication mechanisms.<ref>{{cite web |last1=Ylonen |first1=Tatu |title=History of the SSH Protocol |url=https://www.ssh.com/ssh/telnet |url-status=live |archive-url=https://web.archive.org/web/20180725073549/https://www.ssh.com/ssh/telnet |archive-date=25 July 2018 |access-date=14 June 2017 |website=SSH home page |publisher=SSH Communications Security, Inc.}}</ref> For example, a large number of industrial and scientific devices only have Telnet available as a communication option.  Some are built with only a standard [[RS-232]] port and use a serial server hardware appliance to provide the translation between the TCP/Telnet data and the RS-232 serial data. In such cases, SSH is not an option unless the interface appliance can be configured for SSH (or is replaced with one supporting SSH).{{citation needed|reason=The provided source only states that telnet is used for legacy applications; the details about legacy systems are all unsourced.|date=April 2025}}

Telnet is commonly used by [[amateur radio]] operators for providing public information.<ref>{{Cite web |title=What is Telnet? {{!}} PDF {{!}} Networking Standards {{!}} Internet Standards |url=https://www.scribd.com/document/514519676/Telnet |access-date=2023-01-12 |website=Scribd |language=en}}</ref>

Despite recommendations against it, security researchers estimated that 7,096,465 exposed systems on the Internet continue to use Telnet as of 2021. However, estimates of this number have varied significantly, depending on the number of ports scanned beyond the default TCP port 23.<ref name="srinivasa2021" />

The Telnet client may be used in [[debug]]ging network services such as [[SMTP]], [[Internet Relay Chat|IRC]], or [[HTTP]] servers, to issue commands to the server and examine the responses. In this case, when the Telnet client establishes a TCP connection to a port other than the standard Telnet server port, it does not use the Telnet protocol, and can be used instead to send and receive data over the TCP connection directly.<ref name="sysadmin.md">{{Cite web |title=Debugging server services with telnet |url=https://www.sysadmin.md/debugging-server-services-with-telnet.html |access-date=2023-01-12 |website=www.sysadmin.md |language=en}}</ref>{{Better source needed|reason=The website shown demonstrates such usage, but does not discuss how it works or that it is widely used.|date=April 2025}}