I got a very simple test I am writing to do a client server communication sample in .NET Standard (1.4).
At runtime I got a type load exception as follows:
System.IO.FileNotFoundException: ‘Could not load file or assembly ‘System.Net.Sockets, Version=220.127.116.11, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. The system cannot find the file specified.’
My .NET Standard server class
public class NetworkServerEcho
public async void Start(int port)
var server = new TcpListener(new IPEndPoint(IPAddress.Any, port));
var connection = await server.AcceptSocketAsync();
var t = Task.Run(() => HandleConnection(connection));
private async void HandleConnection(Socket connection)
Nuget dependency: System.Net.Sockets (4.3.0)
.NET Framework (4.6) / console test app
static void Main(string args)
int port = 5434;
var p = new HelloEcho();
var ser = new NetworkServerEcho(p);
What am I missing?
There is no System.Net.Sockets in the .NET Framework. I was expecting some binding redirect magic that would solve the problem. The .NET Standard System.Net.Sockets package declare it supports .NET Framework 4.6. Sockets are in System.dll on the desktop.