poke capture

8/10/2019 Poke Capture

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PokeCaptureSNCHEZ TORREGROSA, LVARO1405091


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Content

The Idea Network Architecture

Application-level protocol

UDP

Network API

Structure of the Code Structure of the Network

Prediction & Interpolation

Effectiveness

Changes


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The Idea

The game is based on the famous pokemon video games

Two players appear on the scene, they see each other but nothingelse

Their objective is to find the hidden pokeball and then the hiddenpokemon to win the game


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Network Architecture

Peer-to-Peer (few players)

Broadcast (few players)

Hybrid multi-server (Small world)

Hybrid client/server (no scalability required)

The selected arquitecture is clientserver

Both clients need to connect to the server and then will wait until theother player is ready

All the movement, or actions will be sended from the client to the serveand then him will check if the operation can be executed and then wianwer the clients


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Application-level protocol

There are 2 Data Structures that are shared between the client andthe server:

StateMessage Win, lose, Start Game, FirstConnection

GameMessageMovement, Pokeball Collected, Pokemon Collected


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UDP

The application runs with non-blocking UDP sockets. Which means Less reliability (package loss)

Better latency (since TCP deliberately delays and merges packets) butUDP just send them)

Easy to stablish (you dontneed to accept all the connections sinceUDP sockets arentconnected all the time)

Only one socket on the server side instead of a list of connections


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Network API

WinSock Previously used

Rich Documentation

Internet full of examples and discussions about it

Other alternatives

SFML Networking


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Structure of the Code

The main class of the code is called GameClass and handles allthe logic of the game.

There is also an InputClass which handles the input of the playerand a GraphicClass who renders the screen.

After those 3 clases there are data classes such as player, object,levelScene or collision and one important class called Client.


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Structure of the Network

Client The Client is a singleton which 4 methods.

SendStateMessage / SendGameMessage Send to the server the data

ReceiveStateMessage / ReceiveGameMessage Receive a msg structureand returns it to the GameClass

The GameClass is the one that analizes which type of message is and

deals with it, modifying the proper logic to get the game working.


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Structure of the Network

Server First of all it binds the socket and waits for an state message of First

Connect, as son as he gets it he sends the player information to the clientand waits for the other one. Once he has the two clients he sends aGameStart (state Message) message

After that he has 4 methods just like the client for receiving and sendingmessages depending on their type and just wait until he receives somethin

then works with it and send-it back. The situations that he is ready to react are:

Try to find Check if the player is near a hidden object then notifies the client

Try to collect Check if the player has discover the object and is near it

Win / Loose Check if the player has accomplish all the objectives of the gameand ends the game if itscorrect


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Prediction & Interpolation

Linear Prediction When the player moves he sends a message of movement, then he

wontsend a message until he stops moving or changes direction.

The server will notify the clients the new position and then the client wilpredict the movement of the other player

Interpolation

If the client receives a movement message and the new position of theplayer is very different from the previous one the player will move fasteto the right position


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Changes

How to deal with package loss Clients send a secuence number when they send an important message to

the server (such as trying to find or trying to collect)

The server needs to send the same secuence number as an answer

If the client doesntreceive the secuence number it shows a message tellintry again, connection failed

Synchronising animation when idle

Now if the server update the position of the clients clients notice if the otheplayerhasntmade a move since the previous update and modifies hisanimation to an idle animation

Reducing amoung of messages The client only send a message when they change direction of movement

so the server considers that while he doesntreceive a change the player istill moving

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