Build a dial-up ISP server using a Raspberry Pi

Trying to connect an old, dial-up–compatible computer to modern-day broadband internet can be a chore. The new tutorial by Doge Microsystems walks you through the process of using a Raspberry Pi to bridge the gap.

Dial-up internet

Ah, there really is nothing quite like it: listen to the sweet sound of dial-up internet in the video above and reminisce about the days of yore that you spent waiting for your computer to connect and trying to convince other members of your household to not use the landline for a few hours.

But older computers have fallen behind these times of ever faster broadband and ever more powerful processors, and getting your beloved vintage computer online isn’t as easy as it once was.

For one thing, does anyone even have a landline anymore?

Enter Doge Microsystems, who save the day with their Linux-based dial-up server, the perfect tool for connecting computers of yesteryear to today’s broadband using a Raspberry Pi.

Disclaimer: I’m going to pre-empt a specific topic of conversation in the comment section by declaring that, no, I don’t like the words ‘vintage’, ‘retro’, and yesteryear’ any more than you do. But we all need to accept that the times, they are a-changing, OK? We’re all in this together. Let’s continue.

Building a Raspberry Pi dial-in server

For the build, you’ll need a hardware modem — any model should work, as long as it presents as a serial device to the operating system. You’ll also need a Linux device such as a Raspberry Pi, a client device with a modem, and ‘some form of telephony connection to link the two modems’, described by Doge Microsystems as one of the following:

We need a way to connect our ISP modem to clients. There are many ways to approach this:

  • Use the actual PSTN (i.e. real phone lines)
  • Use a PBX to provide local connectivity
  • Build your own circuity (not covered here, as it would require extra configuration)
  • Build a fake PSTN using VoIP ATAs and a software PBX

I’ve gone with the fourth option. Here’s the breakdown:

  • Asterisk — a VoIP PBX — is configured on the dial-in server to accept connections from two SIP client accounts and route calls between them
  • A Linksys PAP2T ATA — which supports two phone lines — is set up as both of those SIP clients connected to the PBX
  • The ISP-side modem is connected to the first line, and the client device to the second line

Doge Microsystems explains how to set up everything, including the Linux device, on the wiki for the project. Have a look for yourself if you want to try out the dial-up server first-hand.

The sound of dial-up

For funsies, I asked our Twitter followers how they would write down the sound of a dial-up internet connection. Check them out.


beta-tester avatar

oh, i missed that modem sound…
i am wondering if an old modem can “talk” with 56k over a modern VoIP line…

i still have my 56k modem somewhere in a box ;)

PS.: does somebody has a phone number of a bulletin board system (BBS) i can call?! :D

pete avatar

You need to go to … His BBS is 20 node, free to use and telnet accessible …

Russ avatar

Cool! Another option is a line simulator (or ringdown circuit) like a Viking DLE-200B provides a rock solid local analog connection. About $110 new, but requires no configuration except plugging a couple if RJ-11 connectors and a power brick

Rob avatar

I recently used a Pi, asterisk, and a softmodem to act as a dial up server for viewdata (V.23) terminals.. No isp-side modem needed! I really ought to write it up properly, but a bit of info is here:

Peter avatar

Another option for getting that old dial up computer on the internet is a serial port to Wifi adapter. Like
“WiFi232” or
“Retro Wifi SI”

Peter avatar

I wonder if someone could make something similar with a PiZero-W

Wesley avatar

You can DIY pretty easily with a cheap ESP-01 and a TTL RS-232 converter…the right firmware and you ATDT{} and you’re telnetting from an old PC. Probably even cheaper than a Pi Zero W. I did it myself pretty easily, though I haven’t ever gotten around to tying it together to be able to connect it to RS-232 serial, but you can get pre-built adapters pretty cheap too.

Cody Griffin avatar

The guys in the DreamPi community have been doing this for years now using a Raspberry Pi, open source software, a USB modem, and of course a Dreamcast.

Filip Š avatar

I have idea for some project.

Is it possible to use Raspberry Pi as normal phone server? So you would be able to connect two normal (not VoIP) phones to it and they could communicate with each other. Something like real ISP servers that are used for land-line phones. There could maybe even be support to dial some number to talk to Google Assistant.

Actually I mean two things with this. First is normal cable digital land-line phone and second is old analog phone. It would be interesting if you would be able to call each other.

Pete avatar

In the 80s(Pre-internet) I would get home from school and call a local BBS (Bulletin Board System)
It was usually run by some guy in high school. Only one person could connect to it at a time. A great old movie about this is war games. I actually had a war games dialer that would call phones #s for me when I was at school. If it connected to another computer then it would log the number for me.

C avatar

Can’t make a RPi into a PBX for the conversion from modem to internet? Missing a ton of instructions.

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