If you just want to test if something is listening on a port, no need to specify the "telnet" protocol - using curl normally with the verbose option will still

If you just want to test if something is listening on a port, no need to specify the "telnet" protocol - using curl normally with the verbose option will still tell you whether the port is open, though it'll error out later down the path when it doesn't get the expected HTTP response if probing a non-HTTP port.