This is more or less a message queue, one side (client) sends a message, the other side (worker) receive and act on it. But structured around the common use cas

This is more or less a message queue, one side (client) sends a message, the other side (worker) receive and act on it. But structured around the common use case of someone submitting a "job" to be performed(whenever possible, or at a certain time) and workers picking up and performing the job, reporting back the outcome. "ping" here is just a message, not the name of a system command/executable - in this case the worker receives the "ping" request, and just replies with a "pong" message - both sides are code you need to write. You can encode whatever you want in the payload, json, simple plaintext - it's up to the client and the worker to agree on the meaning.