File transfer via modem: Summary of responses

Date: Tue Jan 02 1990 - 15:23:00 CST

There were *many* responses to my request for advice on copying files
between Suns using a dial-up connection. Thanks to all who responded.


The following people recommended kermit, primarily because it is
available on a wide variety of machines. Kermit's main disadvantage is
that current versions are slow because they wait for each packet to be
acknowledged before sending the next.

  mike at NUADA.LBL.GOV (Michael Helm)
  Randy Fischer <>
  guyton%condor at RAND.ORG
  Mike Howard, Hughes Research Labs AI Center <
  cohen at GUMBY.ECS.UMASS.EDU (Marc Cohen)
  amdcad!diablo!randyd at AMES.ARC.NASA.GOV (Randy Devol)
  Ted Frohling [thanks for the offer, Ted]
  cohesive!kla!serendip!pat at SUN.COM (Pat Lashley)
  Anthony A. Datri <convex!datri at UXC.CSO.UIUC.EDU>
  stutes at SUN207.NAS.NASA.GOV:
  mark at JTSV16.JTS.COM (mark booker)

Ken Rossman <ken at WATSUN.CC.COLUMBIA.EDU> sent this note:

> I'd recommend [Kermit] (but then, I'm biased). :-)
> Actually, Kermit has been extended to include sliding windows, but I
> believe most implementations still have not included this as yet...


Many people suggested using uucp:

  Ed Anselmo <anselmo-ed at YALE>
  gcm!amadeus!dal at UUNET.UU.NET (Dan Lorenzini)!jsalmi at MMM.SERC.3M.COM (John Salmi)
  bill at JTSV16.JTS.COM (Bill McSephney)
  mark at JTSV16.JTS.COM (mark booker)
  jlp at HAMBLIN.BYU.EDU (Jan L. Peterson)
  Jan Berger Henriksen (jan at EIK.II.UIB.NO)
  Henry Troup <HWT at BNR.CA> (H.W.)
  pml at CACS.USL.EDU (Patrick M. Landry)

Most of the messages were similar to

> geez - i hope that this isn't too obvious, but how about uucp?

Uucp is of course the obvious choice if you are communicating between
unix systems and if you can get the sysadmin at the other end to help
you out. I got this advice from stutes at SUN207.NAS.NASA.GOV:

> ... Your system admin could put your host in his table with a never
> poll indication and then you could do the polling from your end, ...


Zmodem (rz/sz, from uunet:comp.sources.unix/volume12) was also
recommended by several people:

  Anthony A. Datri <convex!datri at UXC.CSO.UIUC.EDU>
  nuchat!abbadon at CS.UTEXAS.EDU (David Neal)
  Wilson H. Bent, Jr. ... att!hoh-2!whb (whb@hoh-2.ATT.COM)
  Svante Lindahl <Svante.Lindahl at FRONT.SE>

I had read the following entry in the man pages distributed with rz/sz,
and incorrectly assumed that tip would have the same problems as cu. As
most people pointed out, tip's ~C command works just fine with zmodem.

     Calling rz from most versions of cu(1) doesn't work because
     cu's receive process fights rz for characters from the

Eric ? (portal!!ead at SUN.COM) gave these instructions:

> using rz and sz, transfer a file from a remote unix machine
> to your sun as follows:
> 0) connect to remote.
> 1) at remote prompt, issue "sz foo".
> 2) type "~C"; tip will ask "local command?"; answer with "rz".
> 3) put feet up on desk.

Howard Chu posted a message saying that the source to tip would have to
be recompiled to support the ~C command. This is not the case with the
SunOS version, which apparently works fine as is.


There were also a few other methods suggested:

cohesive!kla!serendip!pat at SUN.COM (Pat Lashley):

> In any case, I would advise atob/btoa over uuencode. The output file size
> is only 20% larger than the input, instead of uuencode's 100%; and I think
> that there is some checksumming.

  [The SunOS version of uuencode only expands by 35%.]

> DNET was developed for the Amiga by Matt Dillon. It supports
> unix-unix, Amiga-Amiga, and Amiga-unix communication. The connection
> provides unlimited (well, more than you would want) simultanious reliable
> logical connections (like SL/IP); so you can download and still
> maintain your interactive terminal session. Best of all, it can be
> installed without superuser privileges.

Mike Squires <sir-alan!mikes at UUNET.UU.NET>:

> There's a PD implementation of uucp for PC's - UUPC. It's available from
> a variety of sources, including uunet (ftp'able). The most recent version
> was called "interim.arc" the last time I looked.
> There's also a Fido <--> uucp link called UFG (last version I saw is
> v1.03). This connects a Fido BBS to netnews.

  [Thanks Mike; these aren't needed for Suns, but others might be interested.]


> I've been using xcomm/xcmalt, a communications package for unix boxes.
> It allows using external programs to do file transfers. The latest
> version is available on anonymous ftp.

Anthony A. Datri <convex!datri at UXC.CSO.UIUC.EDU>:

> I think there was a package called comm or pcomm distributed over
> comp.sources.unix (or misc) a while ago, I know nothing of it.

  [There are these files in comp.sources.unix:
          volume20/pcomm1.2 I haven't looked at them either.]


DNET sounds great, as it maintains a virtual circuit during file
transfers. I couldn't find it on a quick scan of uunet; I'll look for
it on simtel next.

I plan to use tip/rz/sz, since I can do it without any assistance from
administrators on the remote machines. Otherwise uucp would be the
logical choice.

I have had good luck transferring medium sized files over a good quality
phone line using manual error correction. The algorithm is:

  1) use cpio, compress, and uuencode to create a file on the remote machine.
  2) start up the copy using tip's ~t [take] command.
  3) go to bed. A 100K line file (620K bytes) takes about 8 hours of modem
       time at 2400 baud.
  4) sum the local and remote files. If they are the same, you're done.
  5) If not, split both files into, say, 10,000 line chunks and sum the
       pieces. If only 1 or 2 are bad, split them again into 1000 line
       chunks, sum them, and re-fetch the bad ones.
  6) If there are more than a few errors, punt. Your phone line is too

Again, thanks to all who responded.

     Dave Kemp <>

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