XMODEM through a PTY

[Alex Measday]

Help!  We're running Sun OS 4.0.3 on various Sun workstations; the Sun
workstations are networked.  Hanging off the network is a CMC TranServer
terminal server, which services a number of IBM PC's running PROCOMM at
9600N1 (we TELNET into the machine we want to access).  Our PROCOMM's are
set to emulate VT-100's and our Unix TERM variables are set to "vt100".
MicroEmacs and VI all run just fine, but we're having problems
transferring files from a PC to a Sun.

When my PC was attached to a serial port on the Sun, I had no problems
transferring files at 9600 baud between the two machines.  PROCOMM's
YMODEM Batch was used on the PC.  Steve Grandi's Unix XMODEM program
(version 3.6) was used on the Sun: "xmodem rty" and "xmodem sty <files>"
were the command lines used.  Everything worked beautifully.

Now that my PC is attached to the terminal server and goes through the
network, PC-to-Sun transfers no longer work.  Sun-to-PC transfers work
great.  The communication programs keep timing out during a PC-to-Sun
transfer and eventually the exchange is aborted.  The Unix XMODEM log file
contains the following output after an attempted PC-to-Sun transfer:

            XMODEM Version 3.6
            Command line: ./xmodem rty
            Can't determine line speed; assuming 1200 bps
            Batch Receive Started in text mode
            ----
            XMODEM File Receive Function
            CRC mode requested
            YMODEM Batch Protocol
            YMODEM file name: testopt.c
            YMODEM file size: 1092
            1K packet mode chosen
            Timeout while reading sector 1-8
            1K packet mode chosen
            Timeout while reading sector 1-8
            ...
            1K packet mode chosen
            Timeout while reading sector 1-8
            XMODEM Fatal Error:  Reception canceled at user's request

The problem doesn't appear to be in Steve Grandi's XMODEM program.  The
KERMIT program we have (from Columbia University) runs, but suffers from
frequent timeouts, reducing the effective data rate to about several
hundred bytes per *minute* - plus the end of the transferred file gets
garbaged up sometimes.

The problem apparently has something to do with the use of pseudo-TTY's.
Has any one else had any problem like this?  (Someone had a similar
problem in comp.unix, but, aside from my own, I never saw any follow-up
postings.) Can anyone suggest a solution or point me in the right
direction to look?

                            Many thanks,
                                Alex Measday    ...uunet!pyrdc!isi!alex
                                Integral Systems, Inc.  Lanham, MD