Thursday 3 February 2011

Multiplayer-enabling my Windows Phone 7 game: Day 1

I’m building a game to enter in Red Gate’s Windows Phone 7 App competition. The first challenge I set myself was to build the core of the game in 3 days from a standing start. Then Red Gate moved the goal posts. So I’ve set myself a new challenge: make the game multi-player in 3 days, using Windows Azure for the server side. Here’s Day 1:

9:00 Started researching networking capabilities in WP7. MSDN has a useful summary. In short, HttpWebRequest and WebClient are supported, as are parts of WCF. One notable absence are Duplex Services – so it looks like I’ll be doing my own client side polling. ChannelFactory.CreateChannel is not supported, so service proxies cannot be generated dynamically - they have to be created using Add Service Reference, or slsvcutil on the command line. Since I’m not a great fan of all the boilerplate that the Add Service wizard spits out, I think I’ll give WCF on the client side a miss. This gives me the idea of creating a RESTful service that I can call using plain old HttpWebRequests.

9:16 Given the recent hoo-ha  over Windows Phone 7 data leaks, I think I should do my bit to save bytes and minimise data usage. I'Since I’m quite keen on Google’s Protocol Buffers format, I’m pleased to discovered that ProtoBuf.Net, Marc Gravell's implementation of the Google Protocol Buffers format supports WP7.

9:22 Starting work on a Windows Azure project for testing communication between client and server. It’s neat how the Cloud project in VS 2010 has a Windows Azure emulator.

10:38 Downloaded and built Microsoft's WCF Web APIs Preview 3. This extends the REST support that WCF has, as of .Net 4.0. Using this, and helpful blog post from Jesus Rodriguez, got a test service sending back responses using Protocol buffers. One thing that caught me out was failing to decorate my data contract classes with the [ProtoContract] and [ProtoMember] attributes. The serializer just returned an empty stream without that. Now to get the phone talking to the server.

11:05 An interruption: the boss arrives back in the office with an HTC HD7 for me to test the game on!

Signed up for a developer account to allow the phone to be unlocked for testing my apps. To my dismay, I discovered that I can't unlock the phone for deploying test apps until the publisher verification process has been completed. What?! I can understand why Microsoft would want to check that our company is who it claims it is before it lets us submit Apps to the market place; but to my own phone? I think I know who I am!

11:39 Encountered my first real problem: Windows Azure compute emulator only listens on the loopback address,; this means that the Windows Phone 7 emulator can't talk to it. Seems I’m not the first to have encountered this. I tried a number of solutions:

  • Using NCat, a Port fowarding tool. No joy with this at all.
  • TcpTrace, another kind of port forwarding tool, worked, but not when Fiddler was listening in.

13:00 Thanks to some suggestions from Phil Haack I discovered that Fiddler will do the job on its own (is there anything it can’t do?). Following these instructions, I set up Fiddler as a reverse proxy. This means my WP7 app can connect to MyMachine:8888, and Fiddler will shuttle the traffic to and from the Azure emulator.

13:10 Discovered RestSharp, a library that builds on top of HttpWebRequest to simplify making calls to RESTful services. In particular, it can deserialize the Response bytes into objects for you.

13:17 Trying to write a ProtoBuf deserializer for RestSharp, but Protobuf is throwing  MissingMethodException. It looks like I might have to use pre-built Serialization assemblies

14:40: Following Mark Gravell's post on using Protobuf-net with WP7, I mange to get deserialization of messages working on WP7 by pre-building a serialization assembly. I have to resort to subterfuge to get the resulting Serializer assembly added to my WP7 project: The Add Reference dialog refuses to do it, claiming that the assembly is not a bona-fide WP7 assembly, so have to add it to the .csproj file by hand.

15:00 In order to allow users to setup multiplayer games, I’m going to need to show some kind of UI. WP7 doesn’t allow you to mix and match Silverlight and XNA within one App. I don’t really fancy rolling my own UI library, so I start casting around for one. A helpful post on the XNA forums provides a list libraries for XNA in general, though only a couple of them support WP7.

15:35 Start investigating Nuclex UserInterface library, a UI library for XNA that claims support for WP7. Initially it looks quite promising: I can get it to render a couple of buttons. But I can’t make the buttons respond when I tap them.

17:15. I give up on Nuclex, and look for something else. The most promising looking framework is XPF, from Red Badger. It’s ambitious: it aims to replicate some of the core features of Silverlight for the XNA framework, including layout, data binding and animation. They have nightly builds available now, but they’re only valid for 30 days from the build date, and there’s no word yet on a release date, or indeed what the cost of a license will be. Do I take a chance on it?

What are your thoughts? Have I missed a framework that will save me hours? Get in touch: @samuel_d_jack on Twitter, or by email.


Ojassinha90 said...

yeah...nice post but u could use sockets...??

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