Fix broadcast to listen before sending

src/main/java/fr/insa/clavardator/network/NetDiscoverer.java

@@ -30,8 +30,11 @@ public class NetDiscoverer {
 	public void discoverActiveUsers(String broadcastMessage, ResponseReceivedCallback callback, ErrorCallback errorCallback) {
 		if (responseListener != null)
 			responseListener.stopListening();
-		responseListener = new ResponseListener(callback, errorCallback);
-		broadcastSender = new BroadcastSender(broadcastMessage, errorCallback);
+		responseListener = new ResponseListener((ipAddr, data) -> {
+			broadcastSender = new BroadcastSender(broadcastMessage, errorCallback);
+			broadcastSender.start();
+			callback.onResponseReceived(ipAddr, data);
+		}, errorCallback);
 		responseListener.start();
 		broadcastSender.start();
 	}