Question

I am trying to send data from a C#.NET (Windows Application) program to a Java (Android App) program and vice versa, via TCP connection through Wifi. Till now I am success to send data from Java to C#, but unable to do so from C# to Java.

Following is the Java code, I used to create a connection and receive data:

ServerSocket serverSocket = null;
DataInputStream socketInputStream;
while (true) {
        try {
            String localIPAddr = getLocalIPAddress();
            InetSocketAddress ipEndPoint = new InetSocketAddress(
                    InetAddress.getByName(localIPAddr), 8222);
            serverSocket = new ServerSocket();
            serverSocket.bind(ipEndPoint, 4);
            workerSocket = serverSocket.accept();

            socketInputStream = new DataInputStream(
                    workerSocket.getInputStream());
            inputText.setText(socketInputStream.readUTF());
        } catch (Exception ex) {
            throw ex;
        }
    }

Here getLocalIPAddress() method returns the IP Address of the Android Device.

Following is the C# code in Windows Application to connect to the Android’s IP Address (192.168.1.6) and send data to it:

Socket clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
void button1_Click(object sender, EventArgs e)
        {
            try
            {
                if (!clientSocket.Connected)
                    clientSocket.Connect(IPAddress.Parse("192.168.1.6"), 8222);
                clientSocket.Send(Encoding.UTF8.GetBytes(txtInput.Text));
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

Well, client (C#) is failing to connect to the server (Java) That means data is not leaving from client. But it will, if it get connected. Please tell me what am I missing and where am I mistaken. 🙂

Answer 1

Well, I have solved this myself, but of course Dilberted has helped me a little bit. I thank him for what he has provided. 🙂

Check out the solved Java code below:

ServerSocket serverSocket = null;
Socket workerSocket;
DataInputStream socketInputStream;
try {
    if (serverSocket == null) {
        // No need to get local IP address and to bind InetSocketAddress.
        // Following single line make it very simple.
        serverSocket = new ServerSocket(8222, 4);
        workerSocket = serverSocket.accept();
    }
    // When data are accepted socketInputStream will be invoked.
    socketInputStream = new DataInputStream(
                workerSocket.getInputStream());

    /* Since data are accepted as byte, all of them will be collected in the
    following byte array which initialised with accepted data length. */
    byte[] rvdMsgByte = new byte[socketInputStream.available()];

    // Collecting data into byte array
    for (int i = 0; i < rvdMsgByte.length; i++)
        rvdMsgByte[i] = socketInputStream.readByte();

    // Converting collected data in byte array into String.
    String rvdMsgTxt = new String(rvdMsgByte);

    // Setting String to the text view.
    receivedMsg.setText(rvdMsgTxt);
} catch (Exception ex) {
    throw ex;
}

Note that a separate thread is to be used to run this code in background.