Friday 11 February 2011

Multi-player enabling my Windows Phone 7 game: Day 3 – The Server Side

I’m building a game to enter in Red Gate’s Windows Phone 7 App competition. I built the core of the game in 3 days from a standing start. Now I’ve challenged myself to make the game multi-player in 3 days, using Windows Azure for the server side.  Day 1 was spent getting up to speed with Windows Azure and networking on WP7. On Day 2 I got the UI sketched out. Here’s Day 3:

8:30 Begin the day with excellent news. With barely any badgering at all Red Badger have kindly offered me an non-expiring build of their XPF UI library for XNA. Thanks chaps!

And thanks to everyone who's shown support by tweeting the last couple of blog posts. I can't tell you how motivating it is as I set to work again this morning.

8:45 Microsoft have released the January 2011 Update to the Windows Phone Developer Tools (on the 4th of February mind, but I'll let that pass). This is the one that brings the promised Copy-Paste support and some performance updates. Being the good boy I am, I install it before beginning anything else.

9:32 Staring work on the server. I've never designed anything RESTful before, so I've taken a quick look at a couple of articles: one at quite a high level, and one in a little more detail.  A logical place to begin is starting a game. So what I think I need to do is define a /Game resource on my server, and make it respond to POST requests.

11:45 Hooked up AutoFac on the server so that I can inject dependencies into my REST services.

12:00 A good chunk of the day gone, and I still haven't implemented starting a game. WCF isn't playing nice at the moment: I can't get it to respond to the POST request I'm making to my Service.

12:01 Writing the above fixed the problem! Well, not quite. As soon as I had written that, I thought of fiddling with the UriTemplate on the WebInvoke attribute. Since I was posting a request to the /Games resource, and I had registered my Games service using routes.AddServiceRoute<GamesService>("Games", serviceConfiguration) I thought I could get away without specifying a value for UriTemplate on WebInvoke. Turned out I needed to specify "/"!

12:05 Next: list all available games, so that a player can choose one to join.

12:45 Done! I can now create several games through the Start a Game screen, and see them all listed on the Join a Game screen.

16:15 The afternoon passes in a blur. I’ve added several operations to my service, so that the basic game setup screens are working. This is what I’ve got on the server side:

Resource Http Method Meaning
/Games POST Start a Game
/Games GET List existing games
/Games/{id}/Players POST Join a game
/Games/{id}/Players GET List players belonging to a game

Notice any conspicuous absences? That’s right: there are no operations to support actually playing a game. Where has the time gone? But before I can move on, I should at least check that this service works if multiple devices connect to it.

16:25 Fustrated: the Microsoft Windows Phone 7 emulator is single-instance. How can I test a multi-player game if I can only run one copy of it?! I’ve got to find a way round this.

17:30 Eureka! After a journey deep into the bowels of the Microsoft.SmartDevice.Connectivity API and its associated XML datastore I’ve found a way to have multiple instances of the emulator running at once, and even debug them simultaneously.

Hey! Hang on just a minute: there’s already a post on my blog about that – is someone with a time machine playing around with me here? Smile

But never mind that. My 3 days are up, and all I’ve got to show for it are the game sign-up screens. So where do we go from here? Well, I’m going to make my excuses and plead for an extra day – just one more day, and I’m sure I can get it working!

My excuses:

  • It took me ages to get the Windows Phone 7 emulator talking to the Windows Azure emulator: the good folks at Microsoft haven’t connected the dots here.
  • A good two hours or more of my first day was taken up with the hunt for a working UI library for XNA. Thanks to Red Badger for saving me further frustrating hours.
  • Running multiple instances of the emulator really shouldn’t be that hard.

So what do you think? Can I have another day?


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