How to Monitor or Intercept COMM Data Traffic in Windows 95
ID: Q141230
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The information in this article applies to:
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Microsoft Win32 Device Development Kit (DDK) for Windows 95
SUMMARY
In Windows 95, you may sometimes want to set up a way to intercept all COMM
data passing from any application to and from the hardware in use.
Generally, not all traffic is successfully caught.
MORE INFORMATION
There are five basic ways data and control is passed to VCOMM/COMBUFF:
- Exported protected mode API.
- VCOMM_WRITE_COMM VxD calls used with helper VxD's - 16-bit or 32-bit
applications.
- DeviceIOControl for 32-bit applications.
- int 2F calls used with USER/COMM.DRV - 16-bit applications.
- COMMBUFF for MS-DOS VMs bypasses VCOMM altogether - MS-DOS-based
applications
If you are only hooking one of these, you will eventually miss data in some
application. The INT 2F and COMBUFF are not completely publically
documented, so it isn't a simple job to monitor all data. The best way to
intercept COMM data is to create a miniport driver (see Vcomm.doc and
serial sample and Msports.inf) that would require its own enumerator
(static VxD) to register the miniport with VCOMM. The miniport would
receive the traffic and, on its own, open the actual port to relay through
traffic.
A second solution is to register your custom port driver alone and have it
talk directly to the hardware.
A third solution is to write your own version of Serial.vxd, name it
something different (required) and write an .inf to install it.
Additional query words:
4.00
Keywords :
Version : 4.00
Platform : WINDOWS
Issue type :