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Sending files via COM1 - problem solved!


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I'm trying to send files to an old computer through a serial link connected to COM1 on my Win98SE PC. It should be dead easy, no? Well, I'm having a lot of trouble. The physical link works perfectly and the old computer is receiving all the bytes it is being sent without any errors. The problem is that the apps I've tried either add extra bytes or delete bytes. I want to send binary files so it is vital that the file is sent exactly as it is, with no extras and nothing missing.

Things I have tried so far:

1. Adding Generic / Text Only printer on COM1:

Printing files to this printer results in lots of unwanted bytes added to the data stream. Is there any way to tell the printer driver to send the raw data and nothing else? Choosing RAW in Spool Settings does not help.

2. HyperTerminal

For Transfer -> Send Text File, HT does not send CR+LF properly. The LF is stripped and only CR is sent. A LF without a preceding CR is sent fine. If I do File -> Properties -> Settings -> ASCII Setup, then select Send line ends with line feeds, CR+LF are sent properly. However, this creates a new problem: CR with no LF are converted by HT into CR+LF, which is all right for text files but useless for binary files.

3. Redirecting file output in DOS

The COM1 device does not work in DOS7 nor DOS6.22, so I need a Win98 solution.

I wrote a tiny little program about 60 bytes long on the old computer to receive all the serial bytes. Everything works fine at that end. I can't believe it is so difficult at the PC end. Is there some free utility that will do the job? Thanks for any help.

Edited by diskless
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Thanks for the links, but they won't work for me. The old computer is a Z80 machine running CP/M. :yes:

All I need is a prog to read a file and output all the bytes to COM1, without adding or deleting any. I'm really annoyed with HyperTerminal. Maybe I should look for an alternative, but I don't need stuff like Telnet or dial-up connections as the two machines are only three feet apart.

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Tera Term Pro 2.3 is old, from 1998, but works very well.

Unlike Hyperterminal, it uses an .ini file so defaults can be changed, e.g.

; Port type (serial/tcpip)


; Binary flag for Send File and Log (on/off)


; Default directory for file transfers


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Just for the record, there is an updated version:


TeraTerm Pro Web 3.1.3 - Enhanced Telnet/SSH2 Client

TeraTerm Pro Web is the next generation tool for connecting with remote Telnet and SSH hosts. It is built based on the extremely popular open-source TeraTerm product put out by T. Teranishi in 1999 (click here for original site). In keeping with the original philosophy and spirit of the author, our modified version is completely free!!

Downloads TeraTerm Pro Web works on Windows 95/98, 2000, 2003, XP, and Vista.

Here are the latest TeraTerm Pro Web releases:

version 3.1.3 http://www.ayera.com/teraterm/download.cfm

And the Sourceforge continuation of "old" 2.3:


now version 4.67


Edited by jaclaz
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  • 1 month later...

I'm a little confused by the "problem solved" in the title here, when reading the thread, things seem a little open-ended ...

However, what comes to mind is that file transfer via the Xmodem protocol should be possible at the CPM end, and it's definitely supported by HyperTerminal (under "Send File", not "Send Text File").

I don't know if Kermit protocol is also a possibility with CPM, it's also supported by HyperTerminal.

BTW, to redirect or copy a file from DOS (raw data), I think you need to ensure the CTS and DSR lines are active (high). You may also need the "p" MODE option as in (eg.) :

mode com1:9600,n,8,2,p

copy /b blah.xyz com1:


Edited by jds
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  • 2 weeks later...

I don't think he wanted any kermit/zmodem etc.encoded transfers, just a raw filedump which, indeed, Hypertermial can't do.

I *believe* that the newer version of Hyperterminal (Assuming you can still download it at Hilgraeve's website) allows you to turn off unix/dos text conversion but it's been a long time since I used it.

I only ever used it for dial-up BBS'!!

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I don't think he wanted any kermit/zmodem etc.encoded transfers, just a raw filedump which, indeed, Hypertermial can't do.

Perhaps, but his restriction was really that he needed a solution that was viable for CPM. Using a protocol intended for exactly such "raw" (binary) data transfers, and which includes integrity checking, is what I would call "using the right tool for the job". For example (and going off at a tangent), if you want to FTP something "verbatim", you use binary mode, rather than text mode. The option he was trying in hyperterminal was equivalent to what happens with FTP text mode, intended for console text only. Yet hyperterminal does offer the right tools, some of which are supported in CPM.

BTW, I specified xmodem, not zmodem. The former is surely available in CPM, the latter may not be.

[Edit : I've now checked and in fact, not only are xmodem and kermit available for CP/M, so too is zmodem! Rather a surprise, given the time frames.]


Edited by jds
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