Unable to send data from C# to Java (Android) program

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

After you have launched your android app and it is connected to the wifi, did you try to do a ping to the ip where the application is launched.

ping 192.168.1.6

If the IP is accessible from the workstation where C# app is running, try to perform a telnet on the IP and Port of the android ip, to see whether it works or not.

telnet 192.168.1.6 8222

If either of the two steps fail then could be a problem in the wifi network. As i have noticed many times the firewall of the routers filters out all the ports except 8080 and 80. So you would need to open the ports on the router.