When macOS High Sierra (10.13) was released, the telnet utility disappeared. This has probably been a good move by Apple since telnet is outdated and not a secure protocol; it shouldn't be used in general. However, telnet did serve a useful function - checking if it was possible to connect to a remote server on a particular port. Luckily there is a much better tool for this included in macOS - nc (netcat).


Using nc is simple and it has command line arguments that are very similar to telnet. I like to use the -vz arguments whenever I need to check if a remote server can be reached on a particular port. These arguments make nc have this behaviour...


The result is nc tries to connect to the server and then immediately terminates if it succeeds. Here's an example...




If a connection cannot be established and a timeout is reached the output is like this (timeout can be controlled via the -G option i.e. -G 5)...


If a connection is refused, the output is like this...


-i