cs498gd:networking

Table of Contents

Game Networking

Game Networking

Networking Basics

Networking: shifting bits from point A to point B

Internet Protocol (IP) - Network layer
- The Open Systems Interconnection model (OSI model) defines 7 abstraction “layers” for a communications system.
- Puts data bits into a network packet that tells where the packets need to go
- Not reliable by itself

User Datagram Protocol (UDP) - Transport layer
- Uses IP for addressing and routing
- Divides the bits of a packet into groups and sends them in several successive packets

Transmission Control Protocol (TCP) - Transport layer
- Guarantees reliable delivery in the order in which the packets were sent
- Uses IP for addressing and routing; hence better known as TCP/IP

Socket - An endpoint in the IP protocol for sending and receiving data between networked computers

Packet - A block of data sent over the network
- transmits the identities of the sending and receiving stations, error-control information, and a payload (data or messages)

Port - Where information goes into or out of a networked computer
- Ports for major networked services are standardized.
  - HTTP is port 80, MySQL is port 3306, SSH is port 22, etc.
  - See http://www.iana.org/assignments/port-numbers for list of port numbers

Network Design (Topologies)

Most common: client-server

Other designs:
- Which one of these comes closest to a P2P (peer-to-peer) model?

Networking in Java

Package: java.net.*
- You will almost certainly need the package java.io.* for Java networking
- Useful packages:
  - Socket
  - ServerSocket
Implementing a client: see SocketTest.java
Implementing a server: see SingleEchoServer.java

A Simple Networked Game Example

Download NetworkedGame.zip
- SimpleGameServer.java is a standalone server meant to be compiled and run separately.
- PlayerClient.java is currently set to connect to HOST=10.1.13.147 (cslin13.monmouth.edu).
  - If you run SimpleGameServer on a computer other than cslin13, you'll need to change what HOST is set to in PlayerClient.java.

A Game Server

Manage multiple players
Have some capacity
- routine must exist to determine whether server is full
Add and remove players
Send data to one or multiple players
Process players' inputs

A Game Client

Connect to game server
Read and process data from server
Send data to server (for it to process)
Render the content

Diagnostic Tools

Netcat - The network “Swiss-army knife;” reads and writes data across TCP or UDP network connections
Wireshark - For sniffing and analyzing packets
nmap - Network mapper; determines open ports and server software installed on a machine

cs498gd/networking.txt · Last modified: 2013/11/15 20:25 by jchung