TCP Client In High Volume Application?

I have several services that use UDP messages to send out XML status information which is displayed in an application with a UDP listener. This works well. Some of our services are installed at a different site. The UDP messaging does not cross over the routers. Therefore, I wrote a TCP-UDP forwarder service that listens for the UDP messages at the remote site, then forwards them via TCP to a partner service in our local office. That partner service then re-sends the messages via UDP so we may monitor them.

My problem is that the method that sends the messages via TCP appears to be dropping a lot of the XML messages. When the service gets a UDP message, it enqueues it in a queue object for processing. The enqueue statement is enclosed in a synclock object. A separate thread dequeues the message using the same synclock object and sends it via TCP. Originally, I had the code written so that the TCP Send method instantiates the TCPClient, opens it, does a GetSteam, sends the message with a BinaryWriter, closes the writer, closes the stream, closes the client.

Next, I updated the code to declare the TCPClient at the module level. The send method checked to see if the TCPClient variable was nothing and, if it was nothing, instantiated it and connected it. If it was already instantiated, I just tried to re-use it. I close the TCPClient when the service runs the OnStop method. This way did not work. I get "The operation is not allowed on non-connected sockets." errors.

What is the best strategy for implementing a TCP sender that works in a high volume environment. I only have four services sending UDP messages that need to be forwarded at this time. I eventually will have many more.