PRB: Can't Receive Data When Using MSCOMM.OCX Control

- Standard, Professional, and Enterprise Editions of Microsoft Visual

  Basic, 16-bit and 32-bit, for Windows, version 4.0

SYMPTOMS

While performing serial communications by using the MSCOMM16.OCX or MSCOMM32.OCX control, you can get it to connect and send data, but not receive data.

CAUSE

You do not have the correct handshaking enabled.

RESOLUTION

To resolve this problem when using MSCOMM.OCX, set the RTSEnable property to True or add the following line of code to your program when you initialize the MSCOMM control:

   MSComm1.RTSEnable = True

MORE INFORMATION

The following information on the RTSEnable property comes from the Custom Control Help file (CTRLREF.HLP):

   (RTSEnable) Determines whether to enable the Request To Send (RTS)
   line. Typically, the Request To Send signal that requests permission to
   transmit data is sent from a computer to its attached modem.

   When RTSEnable is set to True, the Request To Send line is set to high
   (on) when the port is opened and low (off) when the port is closed. The
   Request To Send line is used in RTS/CTS hardware handshaking. The
   RTSEnable property allows you to manually poll the Request To Send line
   if you need to determine its state.