Gurux.DLMS for .NET Core failed to initialize net connection

Hi. Great to see Gurux.DLMS now available for .NET Core.
But I can't get it to work right now.

I made a simple .NET Core console app using VS2017.
Get the Gurux.Common, Gurux.DLMS and Gurux.Net via NuGet.
And use a slightly modification of GXDLMSReader taken from the client example for .NET Framework.
Here is my code

================
var Manufacturers = new GXManufacturerCollection();
GXManufacturerCollection.ReadManufacturerSettings(Manufacturers);
var man = Manufacturers.FindByIdentification("lgz");

var dlms = new Gurux.DLMS.Secure.GXDLMSSecureClient();
dlms.CustomObisCodes = man.ObisCodes;

var media = new Gurux.Net.GXNet(Gurux.Net.NetworkType.Tcp, "192.168.0.120", 6001);
media.Open();

var reader = new GXDLMSReader(dlms, media, TraceLevel.Info);
reader.InitializeConnection();
reader.GetAssociationView(false);

if (reader != null)
{
reader.Close();
}
================

The code above works perfectly for .NET Framework.
But for .NET core, it stuck at the line InitializeConnection.
Here is the error detail

System.Net.Sockets.SocketException
HResult=0x80004005
Message=A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied
Source=Gurux.Net
StackTrace:
at Gurux.Net.GXNet.Send(Object data, String receiver)

Any suggestion or any client example for .NET Core specifically?
Thanks.