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Q318832: PRB: Run-Time Error 8015 If You Try to Open the Serial Port

Article: Q318832
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s): 
Keyword(s): kberrmsg kbSerial kbModem
Last Modified: 24-JUN-2002

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SYMPTOMS
========

If you try to open the serial port with Microsoft Comm Control, you may receive
the following error message:

  Run-time error '8015': Could not set comm state, there may be one or more
  invalid communications parameters.

CAUSE
=====

This behavior can occur if a serial printer driver is using the serial port that
you are trying to open.

RESOLUTION
==========

To resolve this behavior, disable the serial printer or attach it to another
port. If you are using Microsoft Windows 2000 or Microsoft Windows XP, create a
virtual COM port.

STATUS
======

This behavior can occur if the serial printer driver is not working correctly,
and is not a problem with the MSComm32 Control.

MORE INFORMATION
================

To work around this behavior, create a new virtual COM port and use it instead
of COM1.

WARNING: If anything else prints on the printer attached to COM1, your program
may not work as expected.

1. Add the following code to the General Declarations section of Form1:

  Private Declare Function DefineDosDevice Lib "kernel32" Alias _</BR>
  "DefineDosDeviceA" (ByVal dwFlags As Long, ByVal lpDeviceName _</BR>
  As String, ByVal lpTargetPath As String) As Long<BR/>
  Const DDD_RAW_TARGET_PATH = &H1

2. Add another Command button to Form1.

3. Add the following code in the Click event of Command2:

  DefineDosDevice DDD_RAW_TARGET_PATH, "COM5", "\Device\Serial0"

4. Change the code on Command1 to open COM5:

  MSComm1.CommPort = 5

5. Run the program, click Command2, and then click Command1.

Steps to Reproduce the Behavior
-------------------------------

1. Install a Generic Text printer, and then connect it to COM1 instead of LPT1.

2. Start a new Standard EXE project in Microsoft Visual Basic. By Default, Form1
  is created.

3. Add the Microsoft Comm Control to the project.

4. Add a new MSComm1 control on Form1.

5. Add a new Command button on Form1, and then insert the following code in the
  Click event:

        MSComm1.CommPort = 1<BR/>
        MSComm1.Settings = "9600,N,8,1"<BR/>
        MSComm1.Handshaking = comNone<BR/>
        MSComm1.InBufferSize = 1024<BR/>
        MSComm1.OutBufferSize = 512<BR/>
        MSComm1.RThreshold = 0<BR/>
        MSComm1.SThreshold = 0<BR/>
        MSComm1.InputLen = 0<BR/>
        MSComm1.PortOpen = True<BR/>

6. Run the program, and then click Command1.

REFERENCES
==========

For more information, see the DefineDosDevice function documentation in the
Microsoft Developer Network (MSDN) under Platform SDK.

Additional query words: Serial Port Unspecified Error

======================================================================
Keywords          : kberrmsg kbSerial kbModem 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600
Version           : :6.0
Issue type        : kbprb

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