Path: utzoo!utgpu!watserv1!watmath!att!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!jarthur!bridge2!mbt
From: mbt@bridge2.ESD.3Com.COM (Brad Turner)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Problem with Xmodem and 3Com terminal server
Message-ID: <2910@bridge2.ESD.3Com.COM>
Date: 3 Nov 90 02:53:25 GMT
References: <9010312149.AA07742@z.nsf.gov>
Organization: 3Com Corp., Mt. View, CA
Lines: 69

mmorse@Z.NSF.GOV ("Michael H. Morse") writes:

>I am having a problem getting Xmodem to work between a Sun workstation
>and a PC running a terminal emulator.

>The PC uses a modem and a dial-up line to communicate, but it cannot
>get to the workstation directly because the workstation has no serial
>ports.  Instead, the PC logs on to some other host, and then uses
>telnet to get to the workstation.

>We have a 3Com terminal server that is normally used in this situation,
>but we've found that Xmodem does not work (the PC nacks everything it
>gets) in this configuration.  However, if the PC logs onto one of our
>Ultrix hosts, and in effect uses it for a terminal server to telnet to
>the workstation, Xmodem works fine.  Subsequent tests have absolved the
>terminal emulator (on the PC) and the xmodem program on the
>workstation, leaving suspicion around the telnet implementation
>on the terminal server.

>I suspect this has something to do with parity, since the ASCII
>characters transmitted by Xmodem, and received by the PC are
>identical.  Has anybody run into a similar problem? Any information on
>how telnet reacts when raw mode is selected would be appreciated.

>Thanks in advance.

>--Mike

>-- 

>Michael Morse                           Internet: mmorse@note.nsf.gov
>National Science Foundation               BITNET: mmorse@NSF
>                                       Telephone: (202) 357-7659
>                                             FAX: (202) 357-7663

Mike,
   From your description above it sounds like you have the following
topology.
                                      Ethernet
                                           |
                                           |
               Phone                       |
    PC--Modem1=========Modem2---TermServer-|
               Line                        |
                                           |
                                           |--WorkStation
                                           |

If this is your topology then you should set up the termnial server parameters
as follows for the duration of the Xmodem transfer:

  FlowControlTo=none
  FlowControlFrom=none
  BreakAction=(EscDTM)
  ECMChar=disable

You can create a macro on the terminal server to do this and another macro to
restore the parameters after the transfer. By default the terminal server
attempts to negotiate a binary connection so the connection is 8-bits wide.
It has been a while since I worked in tech support so let me know if this
doesn't work (I'm winging it from memory.) I know that this can work since
I've configured it and had it running in the past (Xmodem through our CS that
is.)

-brad-
-- 
v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v
Brad Turner |5400 Bayfront Plaza |Mktg.Engr.(408) 764-5261| I speak for myself
3Com Corp.  |Santa Clara CA,95052|mbt@bridge2.ESD.3Com.Com| NOT for my employer