[LrSocket - Win10] Sending messages via sockets

Hi. I have the following problem, which leaves me somewhat flabbergasted.

I've loaded up the LrDevelopController sample plugin in Lightroom and written a c# counterpart to talk to it.

It works as expected, except I can't seem to send even a simple "hello world" string back to the external process.

Let me elaborate:

try
{
while (true)
{
   var buffer = new byte[1024];
   int received = _socket.Receive(buffer, SocketFlags.None);
   if (received == 0) return;
   var data = new byte[received];
   Array.Copy(buffer, data, received);
   var message = Encoding.ASCII.GetString(data);
   // This raises an event
   MessageReceived(message);
}
}
catch (Exception e)
{
Console.WriteLine(e);
}

Now, when I send a message to the plugin (via the appropriate c# sender socket), the plugin responds with "ok". So the Lr sender socket is actually working.

However, if I try a simple sender:send("hello world") ... nothing happens.

I've been digging around and I've found that I should actually append the strings with a new line in order for it to work - so i tried a /r/n. I even tried string.char(10)..string.char(13).

No dice.

This is the sender socket Lr code (I removed the observer, as I don't need automatic reporting of changes in the develop params).

local function makeSenderSocket( context )
  -- A socket connection that sends messages from the plugin to the external process.
  local sender = LrSocket.bind {
    functionContext = context,
      address = "localhost",
      port = sendPort,
      mode = "send",
      plugin = _PLUGIN,
      onConnecting = function( socket, port )
      senderPort = port
      maybeStartService()
      end,
      onConnected = function( socket, port )
      senderConnected = true
      end,
      onMessage = function( socket, message )
      -- Nothing, we don't expect to get any messages back.
      end,
      onClosed = function( socket )
      -- If the other side of this socket is closed,
      -- tell the run loop below that it should exit.
      _G.running = false
      end,
      onError = function( socket, err )
      if err == "timeout" then
        socket:reconnect()
      end
      end,
    }
    return sender
end

And I'm trying to get a reply like this: I send a message from c# in a key, value format and the event looks like:

if key == "sendMessage" then
   senderSocket:send( "Hello world\r\n" )
LrDialogs.showBezel( "fired", 1 )
    return true
  end

Lr shows the bezel, but the console output of the c# part looks like this

>>sent "sendMessage = true"

>>received "ok"

I'm at my wits end. Normally I would go like "f it" and use the observer, but I need to report more than simply the developer parameters, so I really need to send a couple of messages back to the c# app.

Would you kindly point me in the right direction?