一个应用程序中的Server和ServerSocket：不起作用

Question

我试图编写一个小程序，打开服务器，创建连接到该服务器并从中接收消息的客户端。

到目前为止，这是《守则》

public static void main(String[] args) {
final ServerSocket serverSocket;
try {
    serverSocket = new ServerSocket(12345);
    Thread t = new Thread(){
        public void run(){
                try {
                    Socket server = serverSocket.accept();
                    PrintWriter writer = new PrintWriter(server.getOutputStream(), true);
                    writer.write("Hello World");
                    writer.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        t.start();
        Socket client = new Socket("localhost", 12345);
        BufferedReader reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String message = reader.readLine();

        System.out.println("Received " + message);
    } catch (IOException e1) {
        e1.printStackTrace();
    }

}

如果我运行程序，它将一直在readLine（）中等待-因此很明显，客户端不会从服务器收到消息。 有谁知道为什么这行不通？

Answer 1

您的阅读线程正在等待数据流中的换行符。 只需更改服务器即可使用：

writer.write("Hello World\r\n");

您将获得预期的结果。 或者，您可以只关闭服务器套接字，然后当readLine到达数据流的末尾时将返回它。

Answer 2

您应该将readline放入循环中，如下所示：

public static void main(String[] args) {
    final ServerSocket serverSocket;
    try {
        serverSocket = new ServerSocket(12345);
        Thread t = new Thread() {
            public void run() {
                try {
                    Socket server = serverSocket.accept();
                    PrintWriter writer = new PrintWriter(server.getOutputStream(), true);
                    writer.write("Hello World");
                    writer.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        t.start();
        Socket client = new Socket("localhost", 12345);
        BufferedReader reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
            // Check this --------------------------------------------------->
            String message = null;
            while ((message = in.readLine()) != null) {   
                    System.out.println("Received " + message);
                    break; //This break will exit the loop when the first message is sent by the server
            }

    } catch (IOException e1) {
        e1.printStackTrace();
    }

}

您可以阅读该文档以获取进一步的说明： http : //download.oracle.com/javase/tutorial/networking/sockets/