Quoridor Classic Game Manager Kevin Dickerson April 2004

System Overview Goal –Develop a system for managing games of Quoridor Classic over a network –Real-time interactive graphics –Open network protocol Why –To allow students a way to play Quoridor Classic without having to write their own game manager! –Hopefully nicer than old text-mode managers that may have been confusing, hard to use –Simplifies software development process for AI!

The Board Game “Real” board game for two players A typical “western” (tile-based) board game. 9x9 tiles Each player starts with 10 walls Each turn, a player moves his pawn to an adjacent tile, or places one wall on the board. Moves may be timed. Objective is to get to the opposite side of the board first!

Quoridor Classic Game Manager (QCGM) Fully implements the board game Quoridor Classic’s rules for two players! Allows players to play “hotseat,” or through a common network protocol. Allows anyone to write their own AI module to control a client.

Special Use AI students will write their own client software that will communicate with my software. Simplified example of communication: –Client 1: “move up” –Client 2: “place a horizontal wall at tile x, y” –Etc… –QCGM does the validation!

Game Manager Software Has several modes: –Stand-alone Server Mode –Interactive Client/Server Mode –Interactive Client Mode

Stand-alone Server Mode Two remote clients connect to the server. The game may be observed, but not interacted with.

Interactive Client/Server Mode The software acts as both server and client for one or two players. Example: –You are Player 1 (sitting at the server). When it is your turn, you click and drag objects to make your move. –Player 2 is a remote client. Player 2 is controlled via the network through either another instance of QCGM, or by AI software!

Interactive Client Mode Client connects to a remote server running the QCGM software. You observe your opponent’s move until it is your turn. You control only your game piece.

Components

Main Form –OpenGL Pane –Menu Bar –Status Bar Start New Game Form –Host a game Join Game Form –Connect to remote server Console Form –View traffic, messages (Don’t worry, final version will be much less purple!)

Algorithms Used Dijkstra’s algorithm –Finds the shortest path from a source node to all other nodes in a graph. –Complexity: O(E lg V) if no nodes are “sealed off” by walls Where, –|E| is the total number of edges in all adjacency lists –and |V| is the number of vertices (or nodes)

Algorithms Used, cont. Dijkstra’s, continued: –In QCGM, each tile is a node, the board is a directed edge graph. Placing a wall removes an edge! –Chosen because players may “win” by reaching any tile in a row across the edge of the board. Side effect: If no walls left, computer may know who will win before the players do!

Algorithms used, cont. Other algorithms I won’t cover today: Arcball (boring)

Built Using: Microsoft Visual Studio.NET 2003 C# OpenGL (via “Tao Framework,” a C# OpenGL wrapper) Windows Forms GUIs Asynchronous Sockets using TCP/IP

Software Features (i.e. Requirements met) Pretty nice 3D graphics (uses OpenGL) Moveable camera uses “arcball” method Click/drag interface for placing moves Dijkstra’s shortest path algorithm for move validation Sockets using TCP/IP to communicate moves over an open (and documented) network protocol

Difficulties Had This project was a black hole for time! –Spent too much time learning C#, Sockets/Networking, Visual Studio.NET –Development of network model had a tendency to lean towards more complicated than simplified, several classes required rewriting/significant changes –I ended up writing about 90 classes/structures! (Is there such a thing as too object-oriented?)

“Nice to Have” Features that Did Not Make It “Tournament Mode” –A number of clients connect all at once, and are queued to play games. Results are recorded. Cryptography –Would unnecessarily complicate network traffic! Not so nice to have after all…

Changes During Development Ditched internal “game protocol communication” idea, just used OO methods! Ditched message packets early on and just used strings – much easier! Simplified network model (no acknowledgement required)

Things I’d Like to Change A more solid network model. –Right now it is not very forgiving! Errors tend to lead to disconnections. –I would probably use a “difference” network protocol, where the server sends the state of the board, rather than individual moves. Right now, it is conceivably possible for moves to be dropped on the client side.

Things I’d Like to Change (cont.) Better OpenGL Graphics –Not necessary, but adding textures or lighting would be nice! Game Records –Would store in a chess-like move record with tables rather than an array of commands.

Questions?