How to write a service that pings another IS?

How can I write a service that runs on one IS and pings another IS (by host name:port)? That is, one IS wants to know if another IS is running.

I see some references to, but no documentation on it.

You could do this in a Flow service that uses pub.remote:invoke to invoke wm.server:ping on the remote IS. pub.remote:invoke is described in the built-in services guide.

wm.server:ping returns a timestamp if the server is running. Of course this only means that it is accepting connections and could process a very simple request, not that the entire server is healthy.