What does it mean when a web service is asynchronous?

Question

What does it mean when a web service is asynchronous? Is this only used when you call it with Ajax and you have a part on your page that refreshes when the web service is done? Thank you.

Answer 1

I know this is an old topic, but whether a web service is synchronous or asynchronous depends on the design of the web service and has nothing to do with Ajax. An asynchronous web service transaction proceeds like this:

1. The client calls the web service. In the call the client sends a callback end point implemented as a service by the client.
2. The web service returns a "message received" reply. ... (Some other processing occurs) ...
3. The web service completes its task, then calls the callback endpoint provided by the client.
4. The client callback replies with message received.

See Developing Asynchronous Web Services or How to: Create Asynchronous Web Service Methods

Answer 2

The question is whether it's the web service that's asynchronous, or your access to it. In the context of a web page, it's more likely that the service is synchronous, but that it is being accessed asynchronously.

Most likely, the service is being called via AJAX. The call is made to the service, and the page then continues. When the response comes in, either the success or the failure functions are executed, asynchronously.