Bridging between synchronous and asynchronous calls

Question

Hi,

I have a long running process that is kicked off by calls to a one-way web service. When finished the process calls back to the caller with the result. Now, the application expected to be the caller will not be able to set up a callback endpoint so I have to develop something that stays in between the caller and the process. This thing will expose a synchronous web service that will kick off the process and return the result. It will also set up a callback interface and be able to correlate callbacks to open sessions and return the synchronous call.

Any ideas?
   

        Request          One-way 
         ----->          ------>
[Caller]        [Bridge]         [Process]
         <-----          <------
        Response         One-way

Figure 1: Excuse my poor illustration :)