Decompiled code from TcpListener.

TcpListenerTPLWrapper.cs

[HostProtection(SecurityAction.LinkDemand, ExternalThreading = true)]
public Task<Socket> AcceptSocketAsync()
{
  return Task<Socket>.Factory.FromAsync(new Func<AsyncCallback, object, IAsyncResult>(this.BeginAcceptSocket), new Func<IAsyncResult, Socket>(this.EndAcceptSocket), (object) null);
}