how best to use websocktes to communicate with served using an ionic app?

There are a lot of resources if you use the search at the top on this already.

Though my two cents:

I’ve dabbled with making a NodeJS web socket server using the http://socket.io libraries. It is totally worth mentioning however, that if you choose to use web sockets, but specifically socket.io it wraps the protocol into it’s own protocol. It is extremely difficult to use any other language besides web based (what socket.io supports, like javascript) and pass data. I worked with one of my network engineers for almost 3 days trying to get it to work but it just didn’t happen.

If you’re only using web platforms to pass data however, it’s SO easy. You send the call name, with the call data, and the client receives it! Simple as that. They have some great examples on the website and it should work well with angular too.