PC端的XX助手和手机App的通讯原理:

# 把PC端8000端口的数据, 转发到Android端的9000端口上.
adb forward tcp:8000 tcp:9000

什么是转发?

执行命令后, PC端的8000端口会被 adb
监听, 这个时候我们只需要往8000端口写数据, 这个数据就会发送到手机端的9000端口上.

PC端程序

把输入内容发送给8000端口

public class PCClient {
    public static void main(String[] args) throws IOException {
        System.out.println("任意字符, 回车键发送Toast");
        Scanner scanner = new Scanner(System.in);
        while (true) {
            String msg = scanner.next();
            sendToast(msg);
        }
    }
    public static void sendToast(String msg) throws IOException {
        Socket socket = new Socket("127.0.0.1", 8000);
        DataInputStream dis = new DataInputStream(socket.getInputStream());
        DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
        dos.writeUTF(msg);
        socket.close();
    }
}

Android端程序

监听9000端口, 把收到的数据, Toast在屏幕上

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "ServerThread";
    ServerThread serverThread;
    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Toast.makeText(getApplicationContext(), msg.getData().getString("MSG", "Toast"), Toast.LENGTH_SHORT).show();
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        serverThread = new ServerThread();
        serverThread.start();
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        serverThread.setIsLoop(false);
    }
    class ServerThread extends Thread {
        boolean isLoop = true;
        public void setIsLoop(boolean isLoop) {
            this.isLoop = isLoop;
        }
        @Override
        public void run() {
            Log.d(TAG, "running");
            ServerSocket serverSocket = null;
            try {
                serverSocket = new ServerSocket(9000);
                while (isLoop) {
                    Socket socket = serverSocket.accept();
                    Log.d(TAG, "accept");
                    DataInputStream inputStream = new DataInputStream(socket.getInputStream());
                    DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
                    String msg = inputStream.readUTF();
                    Message message = Message.obtain();
                    Bundle bundle = new Bundle();
                    bundle.putString("MSG", msg);
                    message.setData(bundle);
                    handler.sendMessage(message);
                    socket.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                Log.d(TAG, "destory");
                if (serverSocket != null) {
                    try {
                        serverSocket.close();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

运行效果

Paste_Image.png

源码

Android-Pc-Socket-Connection

实际开发中的问题

1. Android端的程序 有可能被干掉
2. adb forward 有可能会被干掉

由于连接不稳定性，判断真正连接成功的方法，只有轮询收发握手数据包：
C发送一个数据包，等待S回复；
C如果收到了S的回复包，说明连通。
如果接收超时，则认为没有连通.
在没有连通的情况下，需要重新建立Socket，并Connect()，然后再尝试握手。