Hello r/vintagecomputing!

I'm not sure what is the right sub to post this, but I wanted to do a write-up after my own trial and error and this place seems to fit. I'm going to talk about setting up a simple dial-up network at home, which accepts an incoming dial-up connection and forwards the traffic over your normal network.

Several guides about this exist, like this one by Doge Microsystems or this one I found over at Vogons. Both have their advantages and drawbacks, and you can check them out if you want to learn more or get some more context on the topic, but I want to do this the simplest way possible (which doesn't involve cutting and soldering phone lines) with just a simple PBX phone system, a single client and a modem-equipped server running Windows XP.

Requirements

Phone system

• An analog telephone adapter (ATA) with minimum two lines - I used the Cisco/Linksys PAP2T which seems to be pretty ubiquitous, but the same company also sells similar models which work just as well like the SPA2102
• A raspberry pi to run the phone system - In my setup, this is a raspberry pi 3 running RasPBX, a free PBX (basically a mini phone switch)

Dial-In Server - This is the server which will accept our incoming calls and translate the dial-up traffic over to the home network

• A machine that can run Windows XP without compatibility issues - I'm using some pretty old late '90s hardware which is more suited for Windows 98 but it can handle this use case just fine. The most important part is that it needs to have...
• a fully functioning modem - Mine is a US Robotics OEM modem on a PCI card.
• Windows XP - with all the networking features installed at setup (you probably don't need them all, I just included everything that had to do anything with networking just in case since it won't harm anything even if we don't use it)
• A way to connect to the internet - I'm using a TP-Link TL-WN823N USB Wi-Fi dongle

Phone System Setup

\\ (If you already have a way to call one phone from another (using a number) within your home, like an already set-up PBX, then you can use that and skip this part)

This part assumes you'll be using a raspberry pi like me. There are other options for a PBX set-up like a linux machine running Asterisk. You can check out this guide where they delve into setting up a PBX on a linux PC.

You need to install RasPBX, the downloads and documentation can be found on their website. Once you flash the image on the SD card you can get into the web GUI by going to raspbx.local in your browser, you don't really need to follow their installation guide.

Once you're in the GUI, set-up two Extensions by going to Applications > Extensions and hitting Add Extension > Add New SIP [chan_pjsip] Extension.

In the following menu, you only need to fill out the User (phone number) (I made my phone numbers 6 digits and they all start with 10, so for instance 102535), Display Name (give it a name like "Server" for the dial-in server and "Client" for the other line) and Secret (password) fields, then click Submit and after that Apply Config in the top right.

Once your two extensions have been added, configure your ATAs : you can follow the "ATA Configuration" part of the Doge Microsystems guide but instead of doing what they're doing for the User ID field, put in the number you came up with for your extension in the RasPBX configuration. For the "Proxy" field, what you can do to save yourself the headache of changing the IP every time your router gives the Raspberry Pi (or the machine which is running your PBX) a new IP, is go into your router settings and assign the Raspberry Pi its own static IP on your network. This way its address won't change from time to time and break your setup until you fix it. Perhaps using raspbx or raspbx.local as an IP (like when you accessed the PBX Web GUI) would work but I'm not sure if the ATA will be able to use it like your browser does.

Once you've followed the steps of both dropdowns from that guide (and done it for both lines), and if you have phone sets at home you can test connectivity between the two by dialing one's number from the other and adding a # at the end (this tells the software to start dialing straight away instead of waiting for more digits since our phone numbers are only 6 digits long). Even if you don't have handsets, you can go in your RasPBX web GUI, then to Reports > Asterisk Info and check in the "Channels" table whether both extensions are marked ONLINE.

Once your phone network is fully set-up, the hard part of the guide is over, onto Windows XP!

Dial-In Server

Assembly and Installation

As I said in the requirements, the Dial-In Server needs to have a functioning modem and uses Windows XP. By "functioning" modem I mean that it's in working condition and is fully recognized by Windows XP and can be used to create an Incoming Connection, if you have drivers specific to your modem then even better but if it works fine with XP's Plug And Play functionality then there's not really a point in going looking for them.

While running the XP install, make sure you chose a Custom installation so that you can manually include all the components that have to do with networking. As I said, I don't think all (or even most haha) of them are needed, but my logic when doing this myself was "Better safe than sorry!" so I included them all with my install.

Connecting to the internet

Once your machine is fully installed and you have a functioning XP environment, you need to set-up the server's own internet access. This depends heavily on your hardware, if you have something more modern with an Ethernet port then that would probably be the best route. As my motherboard doesn't have Ethernet, I went with a USB Wi-Fi dongle made by TP-Link. I personally had a lot of issues with XP not being able to connect to Wi-Fi networks, I had to try pretty much every XP driver on the TP-Link website until I found one which included the TP-Link connection utility - this program takes over most of the connection duties and manages them so you no longer pick the networks from XP's own interface but you do it through the TP-Link software. After installing that and the accompanying driver (there's a single Setup application that does both) my XP machine could connect to the internet reliably and automatically on startup.

Accepting and Routing Calls

The next step is configuring something called PPP or Point-to-Point Protocol which is a TCP/IP protocol used for when computers communicate over a phone line.

Here is where Windows XP shines in comparison with previous versions. With something like Windows 98, you have to go through hoops in order to accept a connection (and you need to manually pick-up when there's a call coming in) and you have to use a software router - this is what they are doing in the Vogons guide linked above. In that case, you cannot have an unattended setup where the server does everything automatically once you power it on and the software they used for the internal router (Winroute) is only a 30-day free trial version so that's how long your setup is gonna last.

With XP, you can do all of this in a much easier way - the Incoming Connections Wizard - this wizard allows you to set-up your machine to, you guessed it - accept incoming connections over Dial-Up using PPP. Here is what you're going to do to set it up:

1. Go to Network Connections
2. On the left (or via the File menu), click "Create a new connection"
3. Hit Next, then "Set up an advanced connection"
4. Select "Accept incoming connections" then hit Next
5. On the next screen, check the box next to your Modem device then hit Next
6. Select "Do not allow virtual private connections" then hit Next
7. In the list of users, unselect all of the pre-existing users and add your own, creating a username and password (I used Test and test) - these will be the username and password you enter from the client connecting over Dial-Up as the credentials "given to you by your ISP"
8. On the next screen, select "Internet Protocol (TCP/IP) from the list and hit Properties
9. Here, you want to manually assign a small range of IP addresses that are outside of your router's DHCP range (for me at least, having it automatically assign IPs didn't work), i.e. the range of IPs your router normally gives devices on your network, in order to avoid potential conflicts. For example, the upper limit of my router's DHCP range is 10.0.1.200 so I told XP to specify TCP/IP addresses from 10.0.1.202 to 10.0.1.205. I also left the checkbox for "Allow callers to access my local area network" checked. After you've done that hit OK, and then Next.
10. Now click Finish and an "Incomming Connections" icon should appear in the "Internet Connections" window, where btw you should also be able to see whatever connection you're using to access the internet from the server. I've noticed that sometimes it doesn't show up there but it seems to be a bug as the computer still answers the phone and accepts the connection

That's it for the server setup! Your Windows XP machine should now answer a call coming into its modem, authenticate the user with the username and password you previously set, and forward all their traffic to the WWW.

Time to Test!

Now that this is all done, you can finally test your dial-up network with your client of choice! The only other functioning machine with a modem I have on hand is an Apple iBook G4, using that I go to Internet Connect, select the modem and enter the previously set (on the server) username and password before clicking "Connect". It is then that I get to hear those glorious modem sounds as both machines establish their PPP connection. On the server side, if the connection is successful, you should see the client showing up in the Internet Connections window as their username and by double clicking you can even see the connection speed and information about how many bites have been sent or received.

Once your connection is established, you can discover the impressive community dedicated to making web resources accessible to old computers over slow connections. There is FrogFind, the search engine for old computers that uses DuckDuckGo to search the web while stripping anything that's not compatible with a '90s system using Dial-Up speeds. 68k.news is a proxy for Google News which functions similarly to FrogFind and allows you to browse the news. You can check both of these out over at ActionRetro's YouTube channel, he built them specifically for this purpose! Other interesting websites that I've visited include theoldnet.com which has a bunch of cool things to do with an old machine on the internet, including a way to view old websites from the '90s, retro.mac84.net which is a website for old Macs on the internet and also has cool resources, and I've even managed to get to the homepage of reddit by using the old, lightweight version old.reddit.com!

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Conclusion

After writing this all down, I realize it's definitely not as simple as I make it out to be in the start hahah. To me, the phone system part is the most complicated and the one that's most likely to deter people from attempting this as it requires extra hardware... However, once you're past that hurdle going the XP way offers a much much more simple setup compared to even the Vogons post, and let's not even mention the Doge Microsystems wiki using complicated linux commands...

Of course, this whole setup is wildly insecure and I do not leave my server running unless I'm actually using it to play around. This is a lot of old hardware with outdated firewalls and protocols so I'm always slightly on edge using it, but as long as you stay safe you should be fine and to be honnest the fun massively outweighs the potential issues!

I've never written a Tutorial before, so I apologize if it's long-winded or confusing at times, but this was a lot of fun to put together. I've been toying with the idea of doing a write-up for a while, and I really believe knowledge like this should be shared even though it's not very useful. I would love to hear from you if you end up trying this, and I'll try to help in case of issues and answer questions but keep in mind that I'm no expert myself so I don't guarantee anything!