title: C# ZMQ Socket.SetSockOpt SocketOpt.LINGER - What is the valid options?
body: <pre><code>        using (var context = new Context(1))
          {
              using (Socket socket = context.Socket(SocketType.XREQ))
              {
  
                  socket.SetSockOpt(SocketOpt.LINGER, 100ul);
  
                  socket.Connect("tcp://somewhere:5566");
  
  
                  string content = "test message";
  
                  socket.Send(content, Encoding.Unicode);
                  string message = socket.Recv(Encoding.Unicode);
                  Console.WriteLine("Received reply: " + message);
              }
          }
  </code></pre>
  
  <p>I've tried longs, ulongs and byte arrays and I can not find a value that does not lead to an "illegal argument" exception being thrown.</p>