Communication between android tablet and PC

Question

I am starting on Android and in my first application I need to establish a communication between and android table a PC. The communication is direct by staqtic IPs as I need that when I have several PCs and tablets each table only communicates with its PC.

The communication from the tablet to the Pc is already working but from the PC to the table I cannot get data transfered

Android side

public class Server implements Runnable 
{
    @Override
    public void run() 
    {
        while (always==true)
        {
            while(start2==false)
            {
            }
            try 
            {
                InetAddress serverAddr = InetAddress.getByName("192.168.173.133");
                updatetrack("\nServer: Start connecting\n");
                //*DatagramSocket socket = new DatagramSocket(SERVERPORT2, serverAddr);/
                DatagramSocket socket = new DatagramSocket(SERVERPORT2);

                byte[] buf = new byte[17];
                DatagramPacket packet = new DatagramPacket(buf, buf.length, serverAddr, SERVERPORT2);
                //*DatagramPacket packet = new DatagramPacket(buf, buf.length);/
                updatetrack("Server: Receiving\n");
                socket.receive(packet);
                updatetrack("Server: Message received: '" + new String(packet.getData()) + "'\n");
                updatetrack("Server: Succeed!\n");
                start2=false;

            } 
            catch (Exception e) 
            {
                updatetrack("Server: Error!\n");
                start2=false;
            }
        }
    }
}    

192.168.173.133 is the table IP and SERVERPORT2 is 4445 When I start the application it remains waiting for data after displaying "Server: Receiving" but

C# code

public static void Main()
{
        IPEndPoint iep2 = new IPEndPoint(IPAddress.Parse("192.168.173.133"), 4445);
        string hostname = Dns.GetHostName();
        byte[] data = Encoding.ASCII.GetBytes(hostname);
        sock.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1);
        sock.SendTo(data, iep2);
        sock.Close();
}

I suppose that it is any silly think I am forgotten but after reading many forums and books I am stopped on this point

Any advise will be welcome

Answer 1

You use UDP connection and socket.receive(packet) doesn't wait for packet. If there isn't packet in the buffer this operation throw exception. Try to change your code to:

@Override
    public void run() 
    {
        while (always==true)
        {
            while(start2==false)
            {
            }
            try 
            {
                InetAddress serverAddr = InetAddress.getByName("192.168.173.133");
                updatetrack("\nServer: Start connecting\n");
                //*DatagramSocket socket = new DatagramSocket(SERVERPORT2, serverAddr);/
                DatagramSocket socket = new DatagramSocket(SERVERPORT2);

                while (always==true)
                {
                 try{
                byte[] buf = new byte[17];
                DatagramPacket packet = new DatagramPacket(buf, buf.length, serverAddr, SERVERPORT2);
                //*DatagramPacket packet = new DatagramPacket(buf, buf.length);/
                updatetrack("Server: Receiving\n");
                socket.receive(packet);
                updatetrack("Server: Message received: '" + new String(packet.getData()) + "'\n");
                updatetrack("Server: Succeed!\n");
                start2=false;
                }
                catch(Exception ex) {ex.printStackTrace();}
                }


            } 
            catch (Exception e) 
            {
                updatetrack("Server: Error!\n");
                start2=false;
            }
        }
    }