PC 端的 XX 助手和手机 App 的通讯原理:

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# 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

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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

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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

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。