Android : MQTT Unable to connect to server when using 3G

When I try to run my app on a 3G connection it tries to connect for about 1 or 2 minutes and then it throws an exception, it works perfectly fine on wifi but not on 3G. I have tried with different peoples phone on different networks. Why wont it connect?

The exception it throws i an MQTT exception

Unable to connect to server

This is the MQTT class that i called it creates a new thread:

    public class MQTTService extends Service {

    ContextWrapper c = this;
    private MqttClient mqttClient;

    public IBinder onBind(Intent intent) {
        return null;
    }


    @Override
public void onStart(Intent intent, int startId) {

        Thread background = new Thread(new Runnable() {
            final String BROKER_URL = "tcp://gateway.thebroker.com:1883";
            final String clientId = "android-client90";

            public void run() {
                Looper.prepare();
                 try{


                    MqttClient mqttClient = new MqttClient(BROKER_URL, clientId, new MemoryPersistence());
                    MqttConnectOptions opts = new MqttConnectOptions();
                    opts.setKeepAliveInterval(600);
                    opts.setUserName("nabin");
                    opts.setPassword("M4rk3r".toCharArray());   



                    Log.e("Before Callback", "Connecting..."); // Code works till here if callback is set then errors galore
                    //mqttClient.setCallback(handler.obtainMessage());
                    mqttClient.setCallback(new PushCallback(c));

                    mqttClient.connect(opts);

                        mqttClient.subscribe("house/pill/notification/bad");
                        mqttClient.subscribe("house/pill/notification/good");
                        mqttClient.subscribe("house/pill/notification/skip");
                        mqttClient.subscribe("house/pill/notification/alert");
                        mqttClient.subscribe("house/pill/notification/snooze");
                        mqttClient.subscribe("house/pill/schedule/response");
                        mqttClient.subscribe("house/pill/nextPill/response");

                        Log.e("CONNECTED!", "COOOONNECTED!!!!!");
                }catch(MqttException e){
                    Log.e("Internet Error", "No connection available  " + e.getMessage() );
                }catch(Exception e){
                    Log.e("ERRRRRORRRRR ", e.getMessage());
                }
            }           
    });  
    background.start();
    }
   }    

Thank you for any help!