多线程-实现一个简单人Echo服务器

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实现一个简单的Echo服务器

服务器端监听服务端的到来，当监听到客户端到来之后，将创建一个线程去处理客户端Socket

服务器端：

public class MultiThreadEchoServer {

    private static ExecutorService es = Executors.newCachedThreadPool();

    /**
     * 处理客户端socket
     */
    static class ClientHandler implements Runnable {
        private Socket clientSocket;

        public ClientHandler(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }

        @Override
        public void run() {
            try (
                    InputStream in = clientSocket.getInputStream();
                    OutputStream out = clientSocket.getOutputStream();
                    BufferedReader br = new BufferedReader(new InputStreamReader(in));
                    PrintWriter pw = new PrintWriter(out, true);
            ) {
                long start = System.currentTimeMillis();
                String line = null;
                while ((line = br.readLine()) != null) {
                    pw.println(line);
                }
                long end = System.currentTimeMillis();
                System.out.println("处理耗时：" + (end - start) + "ms");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(8000);
            while (true) {
                // 监听客户端的到来
                Socket clientSocket = serverSocket.accept();
                // 分配一个线程去处理客户端Socket
                es.execute(new ClientHandler(clientSocket));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

客户端：

public class Client {
    public static void main(String[] args) throws IOException {
        Socket client = new Socket();
        SocketAddress addr = new InetSocketAddress("localhost", 8000);
        client.connect(addr);
        try (

                OutputStream out = client.getOutputStream();
                PrintWriter pw = new PrintWriter(out, true);

                InputStream in = client.getInputStream();
                BufferedReader br = new BufferedReader(new InputStreamReader(in));
        ) {
            // 向服务器发送数据
            pw.println("hello");
            pw.flush();
            // 从服务器读数据
            System.out.println("服务器响应：" + br.readLine());

        }
    }
}

相比单线程中处理Socket，它更好的使用多核CPU，可以尽量多的支持客户端数量，但是它的弱点在于，让CPU进行IO等待，如果客户端发送数据时非常慢，这时服务端一直将等待客户端发送数据完毕，这样以来如果每个请求都这样，将拖慢服务器处理处理，服务器的并发数将大大下降，在极端情况下服务端程序将会拖垮！