第三步 实现信息共享:在Socket上的实时交流
网络的伟大之一也是信息共享，Server可以主动向所有Client广播消息，同时Client也可以向其它Client发布消息。下面看看如何开发一个可以实时传递消息的程序。
设计原理：
服务器端接受客户端的连接请求，同时启动一个线程处理这个连接，线程不停的读取客户端输入，然后把输入加入队列中，等候处理。在线程启动的同时将线程加入队列中，以便在需要的时候定位和取出。
｛源码｝
import java.io.*;import java.net.*;import java.util.*;import java.lang.*;public class Server extends ServerSocket{private static ArrayList User_List = new ArrayList();private static ArrayList Threader = new ArrayList();private static LinkedList Message_Array = new LinkedList();private static int Thread_Counter = 0;private static boolean isClear = true;protected static final int SERVER_PORT = 10000;protected FileOutputStream LOG_FILE = new FileOutputStream("d:/connect.log", true);public Server() throws FileNotFoundException, IOException{super(SERVER_PORT);new Broadcast();//append connection logCalendar now = Calendar.getInstance();String str = "[" + now.getTime().toString() + "] Accepted a connection\015\012";byte[] tmp = str.getBytes();LOG_FILE.write(tmp);try{while (true){Socket socket = accept();new CreateServerThread(socket);}}finally{close();}}public static void main(String[] args) throws IOException{new Server();}//--- Broadcastclass Broadcast extends Thread{public Broadcast(){start();}public void run(){while (true){if (!isClear){String tmp = (String)Message_Array.getFirst();for (int i = 0; i < Threader.size(); i++){CreateServerThread client = (CreateServerThread)Threader.get(i);client.sendMessage(tmp);}Message_Array.removeFirst();isClear = Message_Array.size() > 0 ? false : true;}}}}//--- CreateServerThreadclass CreateServerThread extends Thread{private Socket client;private BufferedReader in;private PrintWriter out;private String Username;public CreateServerThread(Socket s) throws IOException{client = s;in = new BufferedReader(new InputStreamReader(client.getInputStream()));out = new PrintWriter(client.getOutputStream(), true);out.println("--- Welcome to this chatroom ---");out.println("Input your nickname:");start();}public void sendMessage(String msg){out.println(msg);}public void run(){try{int flag = 0;Thread_Counter++;String line = in.readLine();while (!line.equals("bye")){if (line.equals("l")){out.println(listOnlineUsers());line = in.readLine();continue;}if (flag++ == 0){Username = line;User_List.add(Username);out.println(listOnlineUsers());Threader.add(this);pushMessage("[< " + Username + " come on in >]");}else{pushMessage("<" + Username + ">" + line);}line = in.readLine();}out.println("--- See you, bye! ---");client.close();}catch (IOException e){}finally{try{client.close();}catch (IOException e){}Thread_Counter--;Threader.remove(this);User_List.remove(Username);pushMessage("[< " + Username + " left>]");}}private String listOnlineUsers(){String s ="-+- Online list -+-\015\012";for (int i = 0; i < User_List.size(); i++){s += "[" + User_List.get(i) + "]\015\012";}s += "-+---------------------+-";return s;}private void pushMessage(String msg){Message_Array.addLast(msg);isClear = false;}}}运行程序,实现信息的实时广播,用户输入"l"就可以列出在线人员表。
