java_advanced_review(3)补充：利用网络套接字实现类似qq 的控制台通讯

【0】README

1）本文旨在实现 利用网络套接字实现类似qq 的控制台通讯， client 采用telnet and java app， server采用 java app；

2）also， you can check out the source code from https://github.com/pacosonTang/core-java-volume/tree/master/coreJavaAdvanced/chapter3/qq_resembled

3）本代码的问题不足在于 没有实现 server 发送到 多个 client 的 socket 连接，即，server 发送的消息属于群发，而不是 peer to peer  的 发送，如果需要完成这个工作的话，需要 socket 连接池，对于每个 client 都建立相应的 socket，即建立相应的 OutputStream and InputStream；

4）编译本代码，可能会报错（错误：找不到符号），解决方法参见：　http://blog.csdn.net/pacosonswjtu/article/details/51804636

【1】server by java app

public class ServerPlainTest {
	public static void main(String[] args) {
		try {
			ServerSocket ss = new ServerSocket(8189);
			System.out.println("the server has startuped, waiting for connections.");
			while (true) { // accept multiple clients connection request.
				Socket s = ss.accept();
				System.out.println("a client has connected successfully.");
				new Thread(new ReceiveHandler(s, Role.SERVER)).start();
				new Thread(new SendHandler(s, Role.SERVER)).start();
			}
		} catch (Exception e) {
			System.out.println(e);
		}
	}
}

public class MessageHandler {
}

// receive msg.
class ReceiveHandler implements Runnable {
	private Socket socket;
	private Role role;

	public ReceiveHandler(Socket socket, Role role) {
		this.socket = socket;
		this.role = role;		
	}

	public void run() {
		try {
			System.out.println(role + " executes ReceiveHandler.run method.");
			InputStream is = socket.getInputStream();
			Scanner in = new Scanner(is);
			
			// echo client input
			boolean done = false;
			while (!done && in.hasNextLine()) {
				String line = in.nextLine();
				System.out.println(line);

				if (line.trim().equalsIgnoreCase("bye")) {
					done = true;
				}
			}
			// close relative instance.
			in.close();
		} catch (IOException e) {
			e.printStackTrace();
		} 
	}
}

// send msg.
class SendHandler implements Runnable {
	private Socket socket;
	private Role role;

	public SendHandler(Socket socket, Role role) {
		this.socket = socket;
		this.role = role;		
	}

	public void run() {
		PrintWriter pw = null;
		try {
			System.out.println(role + " executes SendHandler.run method.");
			Scanner s = new Scanner(System.in);
			OutputStream os = socket.getOutputStream();
			pw = new PrintWriter(os, true); // autoFlush=true.
			
			if (role.equals(Role.SERVER)) {
				pw.println("from server: you've connected with the server.");
			}

			while (s.hasNext()) {
				String line = s.nextLine();
				pw.println("from " + role + ": " + line);
			}
			pw.println("connection closed successfully. bye!");
		} catch (Exception e) {
			e.printStackTrace();
		}  
	}
}

【2】client by java app

1）source code is as following

public class ClientPlainTest {
	public static void main(String[] args) {
		Socket s = null;
		try {
			s = new Socket("localhost", 8189);
			System.out.println("connection with the server successfully.");
			new Thread(new ReceiveHandler(s, Role.CLIENT)).start();
			new Thread(new SendHandler(s, Role.CLIENT)).start();
		} catch (Exception e) {
			System.out.println(e);
		} 
	}
}

2）console info：

【3】client by telnet (connect with server by telnet localhost 8189)