You've been beaten to the punch: https://devnull-as-a-service.com/
$ telnet devnull-as-a-service.com 9
Trying 2001:19f0:6c01:497:5400:ff:fe69:8cbf...
Connection failed: Connection refused
Trying 45.76.95.197...
telnet: Unable to connect to remote host: Connection refused