WCF - Compact Framework - Pull data from mobile client

Question

Hello guys, I want to communicate xml serialized objects from the server to the client and the other way arround. Now it is (probably) easy to invoke methods from a mobile client (compact framework) using WCF, but is there a way so that the server can invoke methods on the client side or some other way to pull data from the client? I know that callback contracts are not available in the compact framework as you can see here: http://blogs.msdn.com/andrewarnottms/archive/2007/09/13/calling-wcf-services-from-netcf-3-5-using-compact-wcf-and-netcfsvcutil-exe.aspx

Originally I thought of socket programming and of developing this by myself, then someone here mentioned WCF. But it seems like WCF only would work in a non mobile environment as I need callbacks.

Anyone can help me with this? Is it possible to develop a two way communication with a desktop server and multiple mobile clients using WCF, or will I have to do socket programming?

Thanks for any advice or any kind of help!

Answer 1

Even if you go to sockets it might be a bit difficult due to routing, carrier filtering and NAT translations (you've not mentioned what your actual network topology is). This is the reason that most mobile applications have to poll the server, even if it is a "push" paradigm (like Exchange's push mechanism, where the client actually polls).

Generally speaking, unless you're on something like a local wireless network where you have solid, routable, unfiltered network access, the client should periodically call the server and ask if the server has data. If it does, then it pulls the data from the server.

EDIT

Now that we know a little more about your topolgy from your comment, I can steer you a little more. Unfortunately Microsoft has not made it easy for Windwos CE devices to host services (WCF or otherwise). There is, in theory, the required infrstructure to build up your own WCF channel and actually host a service, but it's not a trivial task. I looked into it quite some time ago and figured it was a couple months of work and that would have been with the assistance of someone in Redmond that knew how the existing Exchange channel works.

Personally I'd opt for hosting a REST-based web service using our Padarn web server because it's simple to do and I've done it for quite a number of clients now. I realize that it's a little self-serving to propose Padarn as a solution but the entire reason I implemented custom IHttpHandlers in Padarn was because I couldn't find anything else out there that really provided any easy way for a CE device to host it's own services and it's a problem we often have to provide a solution for.

The other options would be things like a proprietary socket solution, hosting an FTP server on the device, using the (abhorrent, IMO) MS-provided HTTP server with ISAPI, Telnet or something along those lines. All of them seem either a hack, a lot of work or both.

Answer 2

at ctacke

Thank you for your help. I actually stumbled across your Padran web server before.Havent really checked it out yet. But I definitely will do that later on. Anyway, a socket solution does not seem that bad at the moment. In the meanwhile I figured that it is quite easy to send data from multiple clients to a 'socket server'. If I can manage those connections somehow I can send data back to the clients. And then I would have to come up with some kind if protocol which handles the data or commands I send over the network... I guess the hardest part would be to make up such a protocol as I do not have a clue about that atm...