Telnet is obsolete for testing ports

On recent versions of Windows, neither the telnet client nor the telnet service is installed by default, but they are still available as features.

Telnet service and client as features

Years ago, they were used as a terminal service system to manage remote hosts.

Currently, a lot of people are still using the telnet client to test if a TCP port is open.

But starting with Windows Server 2012 R2 and Windows 8.1 you don’t need Telnet anymore to achieve this because there is now the Test-NetConnection cmdlet.

Similar to Test-Connection, the Test-NetConnection cmdlet sends an ICMP Echo request (PING) and in addition, if you add the -port parameter, it tests if the TCP port is open.

Test-NetConnection with the -Port parameter

More about

Test-NetConnection (Microsoft Docs)

Telnet (Wikipedia)

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