Connecting 2 PCs modem-to-modem

I know it can be done, but am having trouble making it work.

The idea is to connect 2 PCs directly through their modems. Not cable modems, ordinary 56K modems. I call it my "Poor Man's Network".

I've found the following pages that describe this operation:

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That second link suggests powering the connecting line with ~24 VDC, but I don't think that's actually necessary. (The first link describes connecting two computeri via modem with no extra hardware needed.)

So when I set this up--2 computeri with connected modems, using HyperTerminal at each end, with the following commands:

o sending computer: ATX3D o receiving computer: ATA

I hear stuff through the speaker on the RX end, typical modem connect tones to start, but I don't hear all that "chirping" usually associated with dial-up connections; just a steady, low tone that lasts for, say,

30 seconds or so, then the connection goes dead and I get "NO CARRIER" at both ends.

Everything seems configured correctly: I've set the speed at both ends to 56K and disabled waiting for dial tone.

So what am I doing wrong here?

Please don't suggest using Ethernet or something else instead. I'm trying to use what's at hand here.

Thanks for any help.

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Reply to
David Nebenzahl
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Do you have to use a modem? Ditch the modems and use a null-modem swizzle cable to connect the RS232 ports. If you have a parallel port, you can use the trialware version of totalcommander and the companion program lptdos to connect using a laplink (swizzle cable) on the parallel ports.

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MUCH faster. Nice thing about that is you can boot a dos floppy and do file transfers from your windows machine to load a computer from scratch.

But lan cards wired or wireless are dirt cheap these days. Drop by my place and I'll GIVE you two...if I haven't pitched them all by now. OOps, I didn't say that...'cause you don't want to know.

Reply to
mike

The maximun speed you should set for is 33.6 kbps analogue.

Above that, the communication relies on connection to an ISP's modem rack port supporting digital network signalling, something that is missing on your back-to-back attempt.

--
Adrian C
Reply to
Adrian C

On 1/2/2010 4:37 PM Adrian C spake thus:

Thanks. I bumped the speed down to 19,200 (I think*); the sounds were different, but still no success.

Couple questions:

  1. Are the sounds one hears on the RX side those of the sending modem, the RX one or both?

  1. * Hard to tell with HyperTerminal what speed is actually being used. I configured to modem to use a maximum speed of 19,200, but HT still said "112xxx" (forget the exact #s) until I went and re-configured the modem, at which time it then said 19200.

This really should work.

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Reply to
David Nebenzahl

Whoa! This brings back memories! Several hundred years ago -- back in the DOS 5.0/6.0 and Windows 3.1 days -- we ran The $25 Network in our SOHO. It used the serial ports on the machines for their connection. IIRC, the drives on all the other machines appeared as 'extra' drive letters on each machine, and a common printer could be shared, as well.

I'd be surprised to find that software sourced anywhere... (I might have it on either a 5 1/4" or 3.5" disk in one of the lower stratums of a basement closet.) Then again, this might be that piece of sotware:

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Another, undated, web page makes reference to the $25 Network. And, straining my failing memory, the address listed seems Very Familiar:

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$25net.htm

All it took was the DOS-based program and an RS-232 cable you could cobble up yourself.

gl & hny Jonesy

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Reply to
Allodoxaphobia

Needing a Supply Voltage may be necessary depending on the type of modems you are using. There are some models that give out enough voltage by themselves, and then there are others that need the extra boost.

Here is a good link for what u are trying to do (it refers to linking a fax and modem, but will work the same for 2 modems

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Regards Peter

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Reply to
Peter Kolbe

Both modems are set for the same mode. One has to be switched so you have 'Answer' & 'Originate' modes.

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lists some of the commands in the old Hayes compatible series.

Some early terminal programs set up the modem for you. Some people just used a freeware 'Bulletin Board' program to get around the problem.

As far as the DC voltage, some modems don't have the telephone line transformer. They use a set of diodes instead. These need enough voltage to forward bias them, but it has to be current limited to a few mA to prevent damage. The DC voltage on a phone line is listed as -48 volts nominal and referenced to ground, but if you were close to the older type central office it was in the low to mid 50 volt range.

You can also use 'Direct Cable Connection' for serial or parallel connection of two computers. The cables are easy to make, and a lot faster than using modems.

Open 'help' in the windows start menu and type cable into the search box for information. I used to use the parallel port version in Dos and Win 3.1 days to install software on some computers. That way I didn't have to install, then remove a CD-ROM drive to install the OS and drivers. It was also useful to run OEM drive software to repair screwed up drives after people tried to do Win 95 installs and messed up the low level format.

Another approach is an external drive enclosure with a USB interface. Pull the one drive and slave it to the other computer.

The simplest though, is a pair of $10 network cards and a ethernet cable.

--
Greed is the root of all eBay.
Reply to
Michael A. Terrell

There are a number of pc-pc connection programs; I use PCanywhere:

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Much cheaper if you shop around. JR

HOME PAGE:

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Reply to
JR North

On Sat, 02 Jan 2010 16:20:44 -0800, David Nebenzahl put finger to keyboard and composed:

Some modems have a transformer based DAA and electromechanical relay, others have a silicon DAA. The latter consists of a host side chip and a line side chip. The line side chip requires loop current to operate.

You can tell whether you have an DAA with a electromechanical relay by muting the modem's speaker and commanding it to pulse dial (while disconnected from the phone line).

ATL0M0DP00000000 (all zeros, no "ohs")

Listen for the clicking of relay contacts.

- Franc Zabkar

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Reply to
Franc Zabkar

On 1/2/2010 9:49 PM Michael A. Terrell spake thus:

This turned out to be the best way to get 'er done. Fuck the modems; turns out I already had the perfect cable in my "box o'snakes", a weird null-modem cable (by Belkin) with *two* sets of connectors on each end (DB-9 and DB-25). Was easily able to get things cranked up to 115200 and xfer files with HyperTerminal.

--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"
Reply to
David Nebenzahl

Sorry for coming in late, but if the computers are in the same room, there's no need for modems, as there is no need to modulate/demodulate. A simple serial-port-to-serial-port connection is enough -- with the right software.

Reply to
William Sommerwerck

Only ONE 'Null Modem' cable? Amateur! ;-)

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Greed is the root of all eBay.
Reply to
Michael A. Terrell

I've done this and it worked for me with two internal winmodems. If you can see the modem board (as in internal modems) watch for a small transformer, if the modem does not have one it may not work without line voltage.

I think it only worked if you issued ATX3D first in one computer and then ATA in the other within a timeout period.

I think you mean the serial port speed here, you can set it to 115000 and it will work. To limit the real modem speed you must use an AT command but if you don't it will negotiate 33.6k.

Reply to
Jeroni Paul

In article , David Nebenzahl writes

I think that's incorrect. You need to provide some line voltage. 12VDC will do it.

I feel sick.

You must have a cable to connect the modem line jacks together. If it has at least 3 cores free, why not use a direct serial-serial connection instead of farting about with modems?

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Reply to
Mike Tomlinson

Mike Tomlinson Inscribed thus:

I belive the modem to modem cable needs to be Xover as well.

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Reply to
Baron

Google "null modem".

Jonesy

Reply to
Allodoxaphobia

Google "This turned out to be the best way to get 'er done" in quotes.

Note the subject title. :-|

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Adrian C
Reply to
Adrian C

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