Q49376: COM Port Time-Out Halts Redirection of CVP to Remote Terminal

Article: Q49376
Product(s): See article
Version(s): 2.20 2.30
Operating System(s): OS/2
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 27-OCT-1989

When using protected-mode CodeView (CVP) under OS/2, there is a
problem with the serial communications (COM) ports timing out after 60
to 90 seconds of inactivity. This time-out makes it essentially
impossible to do remote terminal debugging with CVP. Once the time-out
occurs, no further input is accepted from the remote terminal. The
only workaround is to quit CodeView and begin again, or to do a break
and then restart the redirection to the COM port.

The CodeView Debugger allows redirection of input and output to a file
or device. This procedure is commonly used to set up a remote (dumb)
terminal for CodeView input and output, while the PC screen is used
for displaying the program input and output. The terminal is connected
through a COM port, which eliminates the need for a second video
adapter as is required when using two monitors with the /2 option.
Entering "=COM1" at the CodeView command prompt enables input and
output redirection to the device designated as COM1.

This debugging arrangement works great with CodeView under MS-DOS, but
it becomes unworkable with CVP under OS/2 because the internal calls
that are used to set up the redirection do not account for time-outs
due to inactivity. Thus, if you are entering commands from the remote
terminal at a steady pace, everything proceeds smoothly. However, if you
stop and wait for more than about 60 seconds without doing any input,
the port will time-out and leave you stranded because the keyboard no
longer responds.

In a normal debugging session, it is quite likely that there would be
many instances greater than 60 seconds where input is not yet needed
or desired; therefore, this situation quickly becomes intolerable. The
only way to regain control is to enter CTRL+C at the PC keyboard,
which ends the redirection. At that point, you could enter "=COM1"
again on the PC keyboard to restart the redirection if you so desired.

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