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简介

运用Java套接字我们几乎可以完成一个网络聊天软件的小产品，本文不涉及UI部分，仅对原理部分用代码演示一下。一个可以多人聊天的小功能，在Linux系统上用telnet亲测可用。

服务器代码

package demo0811.demo3;

import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 使用多线程写一个服务器，端口号为9999
 * @author zzw
 *
 */
public class ServerMain {

	public static ArrayList<Integer> ports=new ArrayList<Integer>();
	public static ArrayList<OutputStream> streams=new ArrayList<OutputStream>();
	public static void main(String[] args) {
		try(ServerSocket server=new ServerSocket(9999)) {
			System.out.println("服务器正在运行");
			ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(50);
			while(true) {
				Socket socket = server.accept();
				int port = socket.getPort();
				OutputStream outputStream = socket.getOutputStream();
				ports.add(port);
				streams.add(outputStream);
				newFixedThreadPool.submit(new SocketRunnable(socket,outputStream));
				newFixedThreadPool.submit(new NotifyNewersRunnable(port));
			}
		} catch (Exception ex) {
			System.out.println("无法建立监听服务！");
			ex.printStackTrace();
		} 
	}

}

package demo0811.demo3;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Date;

public class SocketRunnable implements Runnable {

	private Socket socket;
	private OutputStream outputStream;
	public SocketRunnable(Socket socket,OutputStream outputStream) {
		this.socket=socket;
		this.outputStream=outputStream;
	}

	@Override
	public void run() {
		try {
			OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream);
			Date date = new Date();
			outputStreamWriter.write(date.toString()+"\n如发私信，请使用[port]开头"+"\r\n");
			outputStreamWriter.flush();
			int port = socket.getPort();
			while(true) {
				if(socket.isConnected()) {
					InputStream inputStream = socket.getInputStream();
					InputStreamReader reader = new InputStreamReader(inputStream,"UTF-8");
					BufferedReader bufferedReader = new BufferedReader(reader);
					String line;
					while((line=bufferedReader.readLine())!=null) {
						if(line.startsWith("[")) {
							int end=line.indexOf(‘]‘);
							int target=Integer.parseInt(line.substring(1, end));
							int indexOf = ServerMain.ports.indexOf(target);
							if(end<0||indexOf<0) {
								OutputStreamWriter outputStreamWriter2 = 
										new OutputStreamWriter(ServerMain.streams.get(ServerMain.ports.indexOf(port)),"UTF-8");
								outputStreamWriter2.write("您的私信格式输入有误或端口号不存在！\r\n");
								outputStreamWriter2.flush();
							} else {
								OutputStreamWriter outputStreamWriter2 = 
										new OutputStreamWriter(ServerMain.streams.get(indexOf),"UTF-8");
								outputStreamWriter2.write("端口"+port+"私信:"+line.substring(end+1)+"\r\n");
								outputStreamWriter2.flush();
							}
						} else {
							for(int i=0;i<ServerMain.streams.size();i++) {
								try {
									OutputStreamWriter outputStreamWriter2 = new OutputStreamWriter(ServerMain.streams.get(i),"UTF-8");
									outputStreamWriter2.write("端口"+port+"群聊:"+line+"\n");
									outputStreamWriter2.flush();
								} catch (IOException e) {
									e.printStackTrace();
								}
							}
						}
					}
				}
				else {
					break;
				}
			}
			socket.close();
		} catch (IOException e) {
			System.out.println("服务器无法向客户端写入数据！");
			e.printStackTrace();
		} finally {
			try {
				socket.close();
			} catch (IOException e) {
				//不处理
			}
		}
	}
}

package demo0811.demo3;

import java.io.IOException;

public class NotifyNewersRunnable implements Runnable{

	private int port;
	
	public NotifyNewersRunnable(int port) {
		this.port = port;
	}

	@Override
	public void run() {
		int n;
		String str="端口"+port+"上线了\r\n";
		if((n=ServerMain.streams.size())>1) {
			for(int i=0;i<n-1;i++) {
				try {
					ServerMain.streams.get(i).write(str.getBytes("utf-8"));
					ServerMain.streams.get(i).flush();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

Java套接字编程实现群聊与私聊[原理版]

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原文地址：http://my.oschina.net/zzw922cn/blog/490959