ZeroMQ is a great way to quickly and simply send messages between multiple programs running on the same or different computers. It is very simple and robust since it doesn’t need any central server. Instead it talks directly between the programs through sockets, TCP-connections or similar.
ZeroMQ has client libraries for basically all commonly used programming languages, but when testing out that a connection works between e.g. two different machines, it might be good to keep things simple and test just the connection, as simply as possible.