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Old 11-17-2005, 09:25 PM   #1
seraph-seph
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How to connect two pc's via modem? (server = linux, client = windows)


Hi there

Does anybody knows how to connect two pc's using their modems with linux?, acctually the options are:

1. Connecting two pc's, linux as server and windows Xp as client .
2. Connecting two pc's, both machines using linux.

Hope anybody can give me a light.

BTW i'm using slackware 10.2 and the client for sure is using windows xp.
 
Old 11-17-2005, 09:39 PM   #2
GrueMaster
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Assuming you are actually trying to connect two systems ate two different locations via dialup, one machine would have to be set up as a dial in server, the other would actually make the call to connect. Here is a link to how to setup a linux system to be a ppp (Point to Point Protocol) server.

If you are trying to connect two systems sitting next to each other, then you need either a network crossover cable and network cards for the systems (preffered), or a null modem cable. Modems rely on the phone companies switching equipment to handshake with. The last job I worked at had an old tester that would mimic a phone line for testing modem to modem connectivity. It was just a very scaled down version of the phone company's equipment (it only had 4 lines).
 
Old 11-17-2005, 10:52 PM   #3
seraph-seph
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Thanks, It cleared what I was looking for .. I'm traying to connect two remote machines via modem (dialup connection), now I know that I need a PPP server for this task..

Thanks a lot. The website you gave me didn't work as well since it's for redhat 6 (pretty old), but I found another one .. just for those who wants to do the same

Linux PPP server

Anyway ... thanks.. now I have another question... If I run apache server on the client (Ex: IE or Firefox), would I be able to test the server remotely? would I be able to see a website on that linux server? Well I guess I will give answers to that questions when I set up this PPP server.

Bye and thanks again
 
Old 11-17-2005, 11:43 PM   #4
gbonvehi
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I never conneted used a direct modem connection to my machine, but I've seen some lines in /etc/inittab that may interest you:
Code:
# Dialup lines:
#d1:12345:respawn:/sbin/agetty -mt60 38400,19200,9600,2400,1200 ttyS0 vt100
#d2:12345:respawn:/sbin/agetty -mt60 38400,19200,9600,2400,1200 ttyS1 vt100
Basically, uncommenting the lines (and maybe editing it according to your serial port) will let you connect to the terminals with the modem. Once there, you could check the server locally but using some console browser (links/lynx/elinks/w3m).
Of course, if it would be better if you get some sort of PPP support
 
Old 11-18-2005, 12:28 AM   #5
GrueMaster
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Quote:
If I run apache server on the client (Ex: IE or Firefox), would I be able to test the server remotely? would I be able to see a website on that linux server?
Yes, but to a limited extent. You have two ways to really view the web site you are creating on the local machine. One is to just open it as a file (file://<path to web location>/index.html). As long as everything is pointing to a relative path (i.e. ../images/me.jpg), it should work ok. The otherway is to either specify the web url, or use localhost (i.e. http://localhost:80). The real limitations are when trying to see how it functions through your internet connection. If this is going to be setup as an isolated web server for data locally, and the machine that is dialing in, you shouldn't run into too many problems.
 
Old 11-19-2005, 09:15 PM   #6
Slim Backwater
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The trouble is going to be getting the modem to work under linux. It's nearly impossible to buy a modem that will work with Linux. Any modem will not do, you have to buy wisely. Get an old external modem if at all possible. Best possible speed will be 33.6 so don't waste money on anything faster. (one end must be digital to get above 33.6 - and that's usually at an ISP). A USR Courier will probably work fine, if you can find one, or can afford a new one.

http://www.tldp.org/HOWTO/Modem-HOWTO.html

http://www.usr.com/products/business...s&sku=USR3453B

The Windows XP machine should be easy. Configure it with a regular dialup to internet connection, with the phone number of the linux box. Probably using a username/password setup on the linux box, and definately not root, don't even try; alot of programs deny it by default (thinking ftp, telnet)

Once Linux can handle the modem, you need to setup a PPP server and hand out an IP address, default gateway, dns servers, etc to a caller (the Windows XP box).

Back in the pre-Internet days everyone was doing this, so the info must be out there and well documented, somewhere.

Good luck.

Brian
 
Old 11-28-2005, 02:16 PM   #7
retiem
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GrueMaster:

I was just wondering if I could connect my laptop to my PC directly thru an RJ11-to-RJ11 cable between the two modems. I guess the answer is no, is it? Even if I set up a dial in server in one of the computers, this won't work? Wouldn't the modems talk ppp to each other w/o need for the telco's circuit-switched path? Why is this? Why is it necessary the signaling protocol and voltage introduced by the telco equipment if the two modems are connected directly to one another?
I find this to be a really interesting matter! I'm curious about it! Will appreciate any comments!
Regards,
Fred

Quote:
Originally posted by GrueMaster
Assuming you are actually trying to connect two systems ate two different locations via dialup, one machine would have to be set up as a dial in server, the other would actually make the call to connect. Here is a link to how to setup a linux system to be a ppp (Point to Point Protocol) server.

If you are trying to connect two systems sitting next to each other, then you need either a network crossover cable and network cards for the systems (preffered), or a null modem cable. Modems rely on the phone companies switching equipment to handshake with. The last job I worked at had an old tester that would mimic a phone line for testing modem to modem connectivity. It was just a very scaled down version of the phone company's equipment (it only had 4 lines).
 
Old 11-28-2005, 05:16 PM   #8
GrueMaster
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Most internal modems (in my experience) can't handle lease line transmissions. There are external modems that can, and with them, you could possibly do this, but the question is why? If you have serial port access, you could get far better speed using a null-modem cable. Most modems max speed is 56k baud, whereas the serial ports of most systems will easily do twice that. See the leased-line howto if you really want to try this. The site also has a diagram for making a null-modem cable.
 
Old 11-29-2005, 04:22 PM   #9
retiem
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Ok, thanks a lot for shedding some light on this topic!
So, yes, it is possible to connect the two modems directly thru an rj11 cable. However, these ought to be external modems, capable of handling leased line connections. Internal/integrated modems (such as in laptop computers) usually won't work...
As of why would I wanna do this?. Simple: just curiosity! I wanted to learn if it was possible to establish a connection directly between the two internal modems I already got installed. And now that I know all what's required to establish such a connection, I'll never bother... I do know that, if no ethernet connection is available, it will be a lot more functional to network the two computers via an RS232 or USBtoUSB cable. I'll have to make/buy one, though
It is always good 2 learn something new!
Regards,
Fred
 
Old 11-29-2005, 05:04 PM   #10
Darin
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I remember back in the BBS days connecting two computers via modems and an RJ-11 cable. If I recall it correctly, the key was using an init string, as the dial string, that ignored tone detect and trying to dial a number and just opened up the link. With some googling, you may be able to find this information, but if the two computers are in the same room, I'd slap cheap network cards in them to connect them together.
 
Old 11-30-2005, 02:33 PM   #11
retiem
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hmmm interesting... guess I have to keep on googling then, although so far I have not found any accurate info.
Initially that's how I thought it would work, i.e., using an appropriate dial string to start the handshaking between the two modems, and having a ppp dial in server running on one of them... that's why I was asking why do they need a dial tone if they are directly connected to one another?
On the other hand, I'd just like to do this to see that yes, technically it works! I really don't need to network my 2 computers! ...just curious to know if I can make them talk to each other through their internal modems...
Regards,
Fred
 
Old 12-02-2005, 03:38 PM   #12
gargamel
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Quote:
Originally posted by Slim Backwater
The trouble is going to be getting the modem to work under linux. It's nearly impossible to buy a modem that will work with Linux. Any modem will not do, you have to buy wisely. Get an old external modem if at all possible. Best possible speed will be 33.6 so don't waste money on anything faster. (one end must be digital to get above 33.6 - and that's usually at an ISP). A USR Courier will probably work fine, if you can find one, or can afford a new one.
Hmmm. I just got an Agere Softmodem in my laptop working, and use it while I am writing this, with no problem. Agere is the successor of Lucent. Agere/Lucent is used in many laptops, so the chance to get an internal modem to work is a bit better than you describe, although far below 50%. In general good external modems are in fact more reliable.

Regarding USR: Many 3Com/USR modems are very good in data mode, but a nightmare when you want to use their fax functionality. If you are interesting in faxing with Linux, eg with the brilliant Hylafax, I'd recommend to avoid USR/3Com. ELSA is better, but not very robust. The best low-cost Fax Modem I know is the Acer Microlink 56k. Highly recommended, and really reasonably priced.

gargamel
 
Old 12-17-2007, 02:36 PM   #13
lncube
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multiple calls

Hi Guys

I also would like to know if a single modem to the server is capable of handling multiple calls from clients at on goal. If so, how?

To put myself clear; In conventional phone systems if someone is already using the line it signals busy to anyone who tries to connect. Is it the same in PPP?

Last edited by lncube; 12-17-2007 at 02:47 PM.
 
Old 03-20-2008, 06:38 PM   #14
rjofre
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[QUOTE=lncube;2993768

1) a single modem to the server is capable of handling multiple calls from clients?

2) To put myself clear; In conventional phone systems if someone is already using the line it signals busy to anyone who tries to connect. Is it the same in PPP?[/QUOTE]

Answers:
1) No, a single modem handles a single analog telephone line, which in turn, can handle only one call at a time.

2) Yes, the second caller would receive a busy tone, then the calling modem will recognize it, and will hang up accordingly, to redial later (if programmed so). And just to make things clear, the second caller will not have the chance to start ppp anyway, until the first caller disconnects.

Best regards from a long term modem user (not master, just user)
 
Old 03-20-2008, 07:38 PM   #15
michaelk
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AFAIK directly connecting two modems together will not work. You need some kind of telephone line simulator.
 
  


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