Android : My device is not visible on Lan

I have a server running on a local pc and I try to broadcast a udp packet from my phone to find the server. Until a few days the app was working perfect. But now when I try to find the server I get the packets on my pc but when I try to send back the response to my phone i cannot reach it.

Also if I try to ping my phone from my pc I get a "Reply from 192.168.1.3: Destination host unreachable."

BUT!! If i ping from my phone my pc then the phone becomes reachable ( I can ping and communicate with the server) for a while and then unreachable again...

What is going on?

Here is the Server code:

        DatagramSocket socket;
        try {
            // Keep a socket open to listen to all the UDP trafic that is
            // destined for this port
            socket = new DatagramSocket(8888, InetAddress.getByName("0.0.0.0"));
            socket.setBroadcast(true);

            while (true) {
                System.out.println(">>>Ready to receive broadcast packets!");
                // Receive a packet
                byte[] recvBuf = new byte[15000];
                DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
                socket.receive(packet);
                // Packet received
                System.out.println(">>>Discovery packet received from: " + packet.getAddress().getHostAddress());
                System.out.println(">>>Packet received; data: " + new String(packet.getData()));

                // See if the packet holds the right command (message)
                String message = new String(packet.getData()).trim();
                if (message.equals("DISCOVER_FUIFSERVER_REQUEST")) {
                    byte[] sendData = "DISCOVER_FUIFSERVER_RESPONSE".getBytes();
                    // Send a response
                    DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, packet.getAddress(), packet.getPort());
                    socket.send(sendPacket);
                    System.out.println(">>>Sent packet to: " + sendPacket.getAddress().getHostAddress());
                }

            }
        } catch (IOException ex) {
        }

and the client code:

 @Override
protected InetAddress doInBackground(Void... params) {
    InetAddress serverAdress = null;

    // Find the server using UDP broadcast
    try {
        // Open a random port to send the package
        DatagramSocket c = new DatagramSocket();
        c.setSoTimeout(10000);
        c.setBroadcast(true);

        byte[] sendData = "DISCOVER_FUIFSERVER_REQUEST".getBytes();

        // Try the 255.255.255.255 first
        try {
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, InetAddress.getByName("255.255.255.255"), 8888);
            c.send(sendPacket);
        } catch (Exception e) {
        }

        // Broadcast the message over all the network interfaces
        Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface networkInterface = interfaces.nextElement();

            if (networkInterface.isLoopback() || !networkInterface.isUp()) {
                continue; // Don't want to broadcast to the loopback
                            // interface
            }

            for (InterfaceAddress interfaceAddress : networkInterface.getInterfaceAddresses()) {
                InetAddress broadcast = interfaceAddress.getBroadcast();
                if (broadcast == null) {
                    continue;
                }

                // Send the broadcast package!
                try {
                    DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, broadcast, 8888);
                    c.send(sendPacket);
                } catch (Exception e) {
                }

            }
        }
        Log.v("this", "waiting for response");
        // Wait for a response
        byte[] recvBuf = new byte[15000];
        DatagramPacket receivePacket = new DatagramPacket(recvBuf, recvBuf.length);
        c.receive(receivePacket);
        Log.v("this", "got response");

        // We have a response

        // Check if the message is correct
        String message = new String(receivePacket.getData()).trim();
        if (message.equals("DISCOVER_FUIFSERVER_RESPONSE")) {
            // DO SOMETHING WITH THE SERVER'S IP (for example, store it in
            // your controller)
            serverAdress = receivePacket.getAddress();
        }

        // Close the port!
        c.close();
    } catch (IOException ex) {
        Log.v("this", "exception");
    }
    return serverAdress;
}

the client stops at the "waiting for a response" log and then after 10 secs goes to the exception....