TCPClient problem with Windows 2000

I'm working on a project using VB.Net 2002. XP is my development platform the system was file until I test it in Windows 2002 Server.

The program connect to a Moxa NPort server using TCPClient component and the Moxa NPort server connect to a door access controller using RS-232.

The program send commands (in byte()) to the controller and get responds from the controller (in byte() format)

Example:
I send a get transaction command to the controller and it will return the transaction packet (42 bytes length) to the program.

This work fine in Windows XP but in Windows 2000 this transaction packet is chopped of in to 3 packets (14 bytes each name it as a1,b1,c1). Every TCPClient.GetStream.Read only can get the first packet.

In order to get the 2nd packet (b1) the program have to send another get transaction command again. Now I have the data stream will have the new transaction data (named is as a2,b2,c2). If I wanna get (c1) I have to send get transaction command again and so on and on.....

Is there any anywhere to set the packet length in Windows 2000?
I hope I didn't confuse anyone here.

Thanks.

Alex