How to get permissions for UDP in Android 5.0. in Xamarin.forms ?

I have used SocketsForPCL to do UDP communications from Android device to server. When I use Android 4.1.2 I could send UDP packets and I received answer from the server. But when I use Android 5.0.1 and 5.0.2 I am not able to send a UDP message. The server does not receive anything. I use exactly the same code.
I think I need to set some permissions, but how to do that?