Android应用程序与Visual Studio终端之间的TCP连接

如何解决Android应用程序与Visual Studio终端之间的TCP连接

我正在尝试与作为客户端的android应用程序实现TCP通信。该服务器已使用库WS2tcpip.h在Visual Studio中的c ++中实现。然后，客户端应发送一个字符串供服务器接收，然后再次返回。我已经使用也在Visual Studio中实现的客户端测试了服务器，并且能够发送一条消息，表明服务器已收到然后返回。见下图

TCP client and server communication

更新代码

ControlFragment.java

public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_control,container,false); //This inflates the control_fragment layout to this java class.

    startBtn = view.findViewById(R.id.startBtn);
    socketString = view.findViewById(R.id.socketString);

    startBtn.setonClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            BackgroundTask b = new BackgroundTask();
            b.execute("Hello");
        }
    });

    return view;
}

class BackgroundTask extends AsyncTask<String,Void,Void> {
    Socket s;
    DataOutputStream dos;
    String ip,message;


    @Override
    protected Void doInBackground(String... params) {
        ip = "192.168.87.103";
        message = params[0];
        try {
            s = new Socket(ip,9700);
            dos = new DataOutputStream(s.getoutputStream());
            dos.writeUTF(message);
            dos.close();
            s.close();

        } catch (UnkNownHostException e) {
            Log.d(TAG,"doInBackground: UnkNownHostException" + e.toString());
        } catch (IOException e) {
            Log.d(TAG,"doInBackground: IOexception" + e.toString());
        } catch (Exception e) {
            Log.d(TAG,"doInBackground: Exception" + e.toString());
        }

        return null;
    }
}

现在，按下按钮后，我看到客户端已连接到服务器，但是它立即断开连接，如下图所示。

TCP connection

我认为错误在于下面的代码。服务器似乎什么也没收到。

int bytesReceived = recv(clientSocket,buf,4096,0); //Returns the number of bytes received
    if (bytesReceived == SOCKET_ERROR)
    {
        cerr << "Error in recv(). Qutting" << '\n' << endl;
        closesocket(clientSocket);
        WSACleanup();
    }
    if (bytesReceived == 0)
    {
        cout << "Client disconnected " << '\n' << endl;
        break;
    }

我已经在清单中包含了互联网许可。希望这是有道理的，并预先感谢您。