A service that dynamically listens for a XML response

Question

Greetings my peepz.

 

The problem for the day is hereby ready for you.

 

My next project at my workplace is as usual, something I have never tried before.

 

The problem has two parts and it is the second part that need your help:

part 1:

Send an XML request via web service to an adress, which is pretty simple

part 2:

The company I send the XML request to is going to send me an XML response which I will have to decipher and handle accordingly. This is however not the problem either, the problem is that I don't know, at all, when the XML response will arrive. Normally the XML response arrives immediately, but not in this case. It can take hours or even days, I don't know. All I know is that is that the sender will "push" the XML response. Normally i "pull" any XML response I wnat, but not in this case. I somehow need a service of sorts to dynamically listen/await for this XML response which I then will handle accordingly.