SOAP web service callback architecture?

Question

I am quite new to web services, JAX-WS etc. so maybe noob question...

So, I want to implement a web service to make two systems communicate. The \"client\" system is

Answer 1

For those getting here from search engines:

You can use a WebHook for Web APIs nowadays, which works essentially as OP described.

In REST for example, the client will have an HTTP endpoint itself that is dedicated to receiving POST events/notifications from the actual server. The client registers his endpoint with the actual server by giving it an URI on his notification endpoint. From that point on, the actual server can POST to the client’s notification endpoint. It is essentially a convoluted callback, if you are familiar with async terminology.

Maybe Java or .Net have libraries for WebHooks by now.

That said, SSE and Websockets standards provide actual push and real-time messages while being compatible with HTTP and most browsers.

Long polling variations were also used in the past, and are now sometimes called Comet as an aggregate.