Vista - Threading problem

I have a device which can talk TCP. It can be sut up both as client and
server simultaneously.
If it is set up as a client, it will send some data when it wants to.
If it is set up as a server, it will respond to messages sent from the
Windows PC.

In my program I set up a thread for endless accepting incoming connections
(this is to handle the client mode of the device):

TcpListener tcpListener = new TcpListener(IPAddress.Any, listenerPortNo);
tcpListener.Start();
while (true)
{
TcpClient remoteTcpClient = tcpListener.AcceptTcpClient();
:
:
remoteTcpClient .Close();
}

I also have a thread for polling the device:

While(true)
{
TcpClient localClient = new TcpClient(deviceAddress, devicePort);
Stream deviceStream = localClient .GetStream();
StreamWriter deviceWriter = new StreamWriter(deviceStream);
deviceWriter .Write("A string which results in a response");
deviceWriter .Flush();
StreamReader deviceReader = new StreamReader(deviceStream);
string response = deviceReader.ReadLine();
tcpClient.Close();
}

The reason why the connections are not kept open is due to the device's
ability of multithreading (??), i.e. it can only handle one connection at a
time.
(And this makes the whole thing a lot less efficient, connections are
"expensive").
The PC software has no control on the timing for when incoming messages from
the device (remoteClient) are received and it shows up that sometimes
the polling thread throws an exception saying that the connection cannot be
made because the target refused it. I think this happens because the
remoteClient are working (a message has been received, i.e. the remoteClient
has been created, but not closed yet.

How can I synchronize these threads to make it safe ?
(Of course I may catch exceptions on the polling and re-try a little later,
but it is not optimal)