Java双向套接字连接(服务器/客户端)

Question

我正在尝试做的是将一些 JSON 从 Android 手机发送到 Java 服务器，这工作正常。 Android/客户端看起来像这样:

                    Socket s = new Socket("192.168.0.36", 12390);
                s.setSoTimeout(1500);

                JSONObject json = new JSONObject();
                json.put("emergency", false);
                json.put("imei", imei);
                json.put("lat", l.getLatitude());
                json.put("lon", l.getLongitude());
                json.put("acc", l.getAccuracy());
                json.put("time", l.getTime());


                BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
                        s.getOutputStream()));
                out.write(json.toString());
                out.flush();
                s.close();

服务器端是这样的:

        try {
        s = new ServerSocket(port);
    } 
    catch (IOException e) {
        System.out.println("Could not listen on port: " + port);
        System.exit(-1);
    }


    Socket c = null;
    while (true) {
        try {
            c = s.accept();
        } catch (IOException e) {
            System.out.println("Accept failed: " + port);
            System.exit(-1);
        }
        try {

            BufferedReader in = new BufferedReader(new InputStreamReader(c.getInputStream()));
                String inputLine = null;
            String result = "";
            while ((inputLine = in.readLine()) != null) {
                result = result.concat(inputLine);  
            }
            System.out.println(result);

正如我所说，所有这些都有效。现在我想在收到来自客户端的消息后将消息从服​​务器发送回客户端。我这样扩展代码，Android/客户端:

                    Socket s = new Socket("192.168.0.36", 12390);
                s.setSoTimeout(1500);

                JSONObject json = new JSONObject();
                json.put("emergency", false);
                json.put("imei", imei);
                json.put("lat", l.getLatitude());
                json.put("lon", l.getLongitude());
                json.put("acc", l.getAccuracy());
                json.put("time", l.getTime());


                BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
                        s.getOutputStream()));
                out.write(json.toString());
                out.flush();

                String inputLine = null;
                String result = "";
                BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));  
                while ((inputLine = in.readLine()) != null) {
                    Log.d(TAG, in.readLine());
                    result = result.concat(inputLine);
                }

服务器端:

        try {
    s = new ServerSocket(port);
} 
catch (IOException e) {
    System.out.println("Could not listen on port: " + port);
    System.exit(-1);
}


Socket c = null;
while (true) {
    try {
        c = s.accept();
    } catch (IOException e) {
        System.out.println("Accept failed: " + port);
        System.exit(-1);
    }
    try {

        BufferedReader in = new BufferedReader(new InputStreamReader(c.getInputStream()));
            String inputLine = null;
        String result = "";
        while ((inputLine = in.readLine()) != null) {
            result = result.concat(inputLine);  
        }
        System.out.println(result);

    PrintWriter out = new PrintWriter(c.getOutputStream());
    out.write("Hello phone");
    out.flush();
    out.close();

在客户端，没有任何东西进来，它卡在

                while ((inputLine = in.readLine()) != null) {
                Log.d(TAG, in.readLine());
                result = result.concat(inputLine);
            }

直到套接字超时(永远不会进入循环)。我认为这可能是一个时间问题，例如服务器过早发出回复，因此客户端从未收到任何东西，但我试图把 out.write("Hello phone");几乎在代码的任何地方，总是相同的结果。会不会是从 ServerSocket 获取的 socket 无法发送数据？我在这里错过了什么，这让我困扰了一整天......

编辑:在 Nikolais 回答后，我尝试了这个(客户端):

                    out.write(json.toString());
                out.newLine();
                out.write("###");
                out.flush();


                String inputLine = null;
                String result = "";
                BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));  
                while ((inputLine = in.readLine()) != null) {
                    if (inputLine.contains("###")) {
                        break;
                    }
                    Log.d(TAG, in.readLine());
                    result = result.concat(inputLine);

                }


                s.close();

和服务器:

                while ((inputLine = in.readLine()) != null) {

                result = result.concat(inputLine);  
                if (inputLine.contains("###")) {
                    System.out.println("received ###");
                    out.println("Hello phone");
                    out.println("###");
                    out.flush();
                    break;
                }

            }

想法是在客户端关闭套接字之前从服务器发送消息。仍然不起作用...有任何提示吗？

Answer 1

在服务器端，您永远无法发送“您好电话”。直到客户端关闭套接字，但此时它是无用的。这是因为 in.readLine() 阻塞，直到数据可用或 EOF，即套接字关闭。

您需要一种摆脱阅读循环的方法 - 发明(或采用)一些应用程序级协议(protocol)，告诉您整个消息已收到。常用选项有定长消息、长度前缀、定界等。