A Simple Chat Server Example

INTRODUCTION

This directory contains a very simple chat server, the server takes input from a socket ("user") and sends it to all other connected sockets ("users") along with the provided name the user was asked for when first connecting.

The server was written to demonstrate the asynchronous I/O API in JDK 7. The sample assumes the reader has some familiarity with the subject matter.

SETUP

The server must be built with version 7 (or later) of the JDK. The server is built with:

% mkdir build
% javac -source 7 -target 7 -d build *.java

EXECUTION

% java -classpath build ChatServer [-port <port number>]

Usage:  ChatServer [options]
    options:
        -port port      port number
            default: 5000

CLIENT EXECUTION

No client binary is included in the sample. Connections can be made using for example the telnet command or any program that supports a raw TCP connection to a port.

SOURCE CODE OVERVIEW

ChatServer is the main class, it handles the startup and handles incoming connections on the listening sockets. It keeps a list of connected client and provides methods for sending a message to them.

Client represents a connected user, it provides methods for reading/writing from/to the underlying socket. It also contains a buffer of input read from the user.

DataReader provides the interface of the two states a user can be in. Waiting for a name (and not receiving any messages while doing so, implemented by NameReader) and waiting for messages from the user (implemented by MessageReader).

ClientReader contains the "main loop" for a connected client.

NameReader is the initial state for a new client, it sends the user a string and waits for a response before changing the state to MessageReader.

MessageReader is the main state for a client, it checks for new messages to send to other clients and reads messages from the client.

FINALLY

This is a sample: it is not production quality and isn't optimized for performance.