java Socket简单聊天实现 —— 实现服务器端向客户端广播内容

重构聊天室案例，使服务端可以将用户的信息转发给所有客户端，并在每个客户端控制台上显示。通信过程如表－2所示：



服务器端：定义一个集合类型的属性，用于存储所有客户端的输出流。在Server的内部类中run方法的最开始处将客户端的输出流存入该集合，之后，每当客户端发送信息后就遍历集合，将信息写入集合中所有的输出流中(相当于将信息转发给所有的客户端)。
package TCPUDP;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class Server {

private ServerSocket serverSocket;
//所有客户端输出流
private List<PrintWriter> allOut;

public Server(){
try{
serverSocket = new ServerSocket(8088);
allOut = new ArrayList<PrintWriter>();
}catch(Exception e){
e.printStackTrace();
}
}

/*
* 线程体：用于并发处理不同客户端的交互
*
*/
class ClientHandler implements Runnable{

private Socket socket;

//构造函数设置为public
public ClientHandler(Socket socket){
this.socket = socket;
}

@Override
public void run() {
PrintWriter pw = null;
try {
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
pw = new PrintWriter(osw, true);
//存入共享集合
allOut.add(pw);

InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is, "UTF-8");
BufferedReader br = new BufferedReader(isr);
String message = null;
while((message = br.readLine()) != null){
for(PrintWriter o: allOut){
o.println(message);
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
//当客户端断线时，要将输出流从集合中删除
allOut.remove(pw);
if(socket != null){
try{
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
}
}

public void start(){
try{
//循环监听客户端的连接
while(true){

System.out.println("等待客户端连接。。。");
Socket socket = serverSocket.accept();
System.out.println("客户端已连接！");

ClientHandler handler = new ClientHandler(socket);
//启动一个线程来完成针对该客户端的交互
new Thread(handler).start();
}
}catch(Exception e){
e.printStackTrace();
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Server server = new Server();
server.start();
}

}

客户端：在客户端中定义一个内部类，并定义线程要执行的任务，这里循环读取服务端发送过来的信息，并打印到控制台。最后，在Client的start方法中启动一个该任务对应的线程，来处理服务器和该客户端之间的通信。
package TCPUDP;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class Client {

private Socket socket;

public Client(){
try {
socket = new Socket("localhost", 8088);
} catch (Exception e) {
e.printStackTrace();
}
}

private class ServerHandler implements Runnable{

@Override
public void run() {
// TODO Auto-generated method stub
try{
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is, "UTF-8");
BufferedReader br = new BufferedReader(isr);
while(true){
System.out.println(br.readLine());
}
}catch(Exception e){
e.printStackTrace();
}
}
}

public void start(){

try{
ServerHandler handler = new ServerHandler();
Thread t = new Thread(handler);
t.setDaemon(true);
t.start();

OutputStream out = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(out, "UTF-8");
PrintWriter pw = new PrintWriter(osw, true);
//创建Scanner读取用户输入内容
Scanner scanner = new Scanner(System.in);
while(true){
pw.println(scanner.nextLine());
}
}catch(Exception e){
e.printStackTrace();
}finally{
if(socket != null){
try{
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Client client = new Client();
client.start();
}

}