Actually Getting Dial-Up To Work
17 Nov 2025 - faintshadows
The last time I tried getting “dial-up” internet going in my retro setup, I was
just using tcpser and standard nix pppd.
I have upgraded now, and dare I say it, I may have a working, real dial-in setup.
What all changed? Getting actual hardware is a good start, plus some happy accidents. In a semi-unrelated project in the local friend group, we were setting up a FreePBX instance so all of us could have saved-from-ewaste Polycom IP phones in our houses as a bit. Also so the one friend could have a playground to mess with PBX software outside of work. An idea came up after we got it working though, how well would this setup handle dial-up? We could just grab ATAs, plug modems in, and call each other.
Initial testing, though, was non-optimal. Modems would connect to each other, but the connection would slowly get out of sync and eventually drop entirely after only a few kilobytes of data. I don’t fully understand what’s going on, but there was something said about framing and the SIP frames of the actual phone ‘network’ weren’t the same size as the PPP packets. Small delays that wouldn’t be noticeable with a voice call would stack up and the connection would fall over. This happened when calling in remotely over a WAN, or in the same room as the PBX server.
We were looking for ATAs to purchase and my partner came across this, an Obihai OBi508vs.
An 8 port ATA, yes, but it turned out to be a little bit more than just that. We bought it to connect up to the FreePBX network we had, but for local use, that’s entirely unneeded. This is an ATA, but also a PBX? It can handle extensions internally, and even has an auto attendant, the beloathed phone menu system. You know, “Press 1 if you are a new customer, press 2 if you have an account number”, that sort of deal.
This thing has a lot going on inside it, I’ll be the first to admit I have no
idea what any of this is. The manual doesn’t do a whole lot in the way of
explaining anything either. I was able to figure out you can dial other
phone ports on itself by doing a pound (#) and the port number. So port 4
would be #4. We don’t have any analog touch tone telephones handy, but
connecting two computers and directly controlling the modem with an ATDT#4
sure worked, the other machine would get a RING and ATA would answer, easy
peasy.
So we can dial in to each other, the Obihai handles all the switching, dial tone
and ring generation. I can type on one end and see it on the other, perfect.
But how do I get onto that sweet sweet Internet? I was getting flashbacks
to my last attempt at this, thinking about setting up pppd and mgetty.
My friend had a better idea though, just use Windows Server. Excitedly, I ran and
grabbed my in box copy of Server 2003 Standard, finally being able to use
this for something real. Threw it on a random laptop I had lying around with
a modem built in, spend all day updating it, and added the Remote Access/VPN Server role.
Okay, it’s live, it sees the modem, but I can’t connect. What gives? Well, despite it being the Windows XP era, there was an attempt at security. By default, connection attempts are blocked. Open Routing and Remote Access, and under Remote Access Policies, add a rule with the policy conditions that a specific group is granted remote access permission. Under Edit Profile, make sure everything looks right, depending on your setup, you may want to allow all the authentication types, so any machine could authenticate, not just Windows clients. I allowed clear text auth and didn’t bother with encryption, since this is effectively a lab environment. Windows will do MS-CHAP auth by default, even on 95, but this allows me to connect anything I can throw at it, more or less.
One thing I should note, Windows will try to be a DHCP server on its own for the remote devices. You can use this if it works for your setup, I disabled it for mine and had it forward requests to my main router.
Give it another dial and…
We’re in! My user testuser is authenticated, I have an IP address, and I’m
sending bits over at 21,600baud. Not too bad, though it’s a strange number, not
a usual dial-up speed. Somewhere between 14.4k and 28.8k. Could be the modem I
am currently connected to, that’s a 28.8 one, but I also get the same speeds on
newer 33.6k and 56k modems.
Nothing’s ever simple. What now? To be completely frank, I have no idea. The running theory is that the Obihai is doing some sort of software switching of the telephone lines, despite the call going from one port to another on the same device. Maybe the UI for it has any hints?
Ah, it thinks this is a fax. ATAs sometimes try to re-encode faxes on the fly to have them better fit a SIP network, and it’s possible it’s doing that here. I did disable all that in the settings, best I could tell. So it may just see any modem traffic as a fax. Despite this though, the connection is rock solid.
I’ve had machines connected for hours at a time (good thing I’m not being billed!), running Windows Update and downloading software, getting the realest experience I can. SMB even works over it, but man is it slow. It’s not even close to faster than writing a floppy with the files on it, or even taking the hard drive and plugging it into a IDE to USB adapter. But that’s not the point! The point is, I can just plug in any machine, dial a number, and have network access. It’s been great to have this for things like my Jornada, which can finally see the Internet under Windows CE! Or the Vaio I have, which has a built in modem. Sure, I could get a PCMCIA Ethernet card, and I do have some, but this requires no extra hardware, just what’s built into the machines.
We’ve tried everything from 1200 baud external serial modems up to an internal modem on an early 2010’s HP EliteBook, it all just works. Slower speeds work fine, anything faster just tops out around 21k. I would like to see about getting a true analog PBX to see if I can do any better that way, or maybe try a dedicated serial modem, maybe the softmodem in this laptop isn’t all that good? Connecting other machines together I get similar speeds though, so it’s hard to really say.
Either way, I’m very happy with this. Era appropriate things load in what I would consider a reasonable amount of time, just a few minutes at worst. I can even attempt to load more modern stuff using WebOne1, a proxy that strips SSL for old machines that can’t support newer TLS. Now, most sites that would require the use of this proxy probably won’t load in something like IE4, but you never know!
I know someone’s probably going to want to ask how much this ATA/PBX costs, and I wish I could say it’s a hidden gem that nobody knows what they have. We got lucky with ours, I think it was around US$30-40 shipped off eBay, but taking a glance as I write, on the cheap end it’s around US$80. However, the OBI504 is the same device, just with 4 FXS ports (phone lines) instead of 8. Those are around US$40-60. This is also very overkill for what I’m using it for, something like an Excelltel SP-208 would be more along the lines of what this sort of project needs. The Excelltel’s are analog, and cost about as much as the 8 port Obihai, US$90~ on Amazon. If I can get my hands on one, I’ll be sure to update this post with the results.
Until next time, ~faint