True multithread VB source code control:
http://www.banasoft.com/DownLoad/BNComm.exe

Banasoft Communication Control is a multithread communication component written by VB completely. It 's compatible with MSComm control and have many enhanced features.

A limitation in MSComm is that we can not use the serial port which number less than 16. Many applications may need 32 or more serial ports to exchange data with MCU. BNComm extend this to the WinNT limitation 256. You can use multiserial link hardware like MOXA freely. Also we are planning to implement parellel port communication in this control next time.