#31 mscomm32 can't read from hub4com

Ilya Basin — Mon, 20 Aug 2018 18:04:44 -0000

The problem was solved by adding the "--octs=off" command line option. For some reason MSComm can't receive events when the handshake is on.

#31 mscomm32 can't read from hub4com

Ilya Basin — Mon, 30 Jul 2018 17:57:16 -0000

I observe that WriteOverlapped::OnWrite is delayed until the mscomm32 reader disconnects and another reader connects to the other side of the pair.

mscomm32 can't read from hub4com

Ilya Basin — Mon, 30 Jul 2018 16:47:36 -0000

There's this emulator http://www.elexol.nl/en/products/espa-tool-uk which's built on VB6 and is using the mscomm32 library for serial io. When it's connected to a simple com0com pair, all is fine, but if this pair is part of a hub4com hub, the 'receive' event is never raised, even when I send just one byte. Other apps can read form this hub without problems.

I was able to reproduce the issue in the custom .VBS script: https://gist.github.com/basinilya/16fd6137ca6809268e869ae3ea634890

My com0com configuration:

COM7 <-> CNCB7
COM8 <-> CNCB8

Buffer overrun enabled. My hub.bat:

hub4com --create-filter=trace --route=All:All --add-filters=All:trace \\.\CNCB7 \\.\CNCB8

The reader script connects to COM8. The writer app connects to COM7. The trace suggests that hub4com is writing something:

2018/07/30 19:46:28.963 CNCB7(0)-(trace)->: MSG_LINE_DATA {[1]:
  04                                               * .                *}
2018/07/30 19:46:28.978 CNCB8(1)<-(trace)-CNCB7(0): MSG_LINE_DATA {[1]:
  04                                               * .                *}

Recent changes to 31: mscomm32 can't read from hub4com

#31 mscomm32 can't read from hub4com

#31 mscomm32 can't read from hub4com

mscomm32 can't read from hub4com