telnet
A terminal-emulation protocol that is widely used on the Internet to log on to network computers. Telnet also refers to the application that uses the Telnet protocol for users who log on from remote locations.
Example:
Microsoft Telnet> o 207.44.188.38 25
Connecting To 207.44.188.38...Could not open connection to the host, on port 25.
An existing connection was forcibly closed by the remote host.
Microsoft Telnet> o 207.44.188.38 25
Connecting To 207.44.188.38...Could not open connection to the host, on port 25.
An existing connection was forcibly closed by the remote host.