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       z80 comm/Technology, (sdf.org), 09/13/2018
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It's time for a meta-monologue about something I wrote 
today[1]. I have a z80 SBC that I want to use for "online 
stuff." In an ideal world, I'd connect my USRobotics modem 
to the thing and dial in to a system, which would give me 
access to sundry online activities. Voila, problem solved 
with just my z80 home computer.

The world, unfortunately, is not my kind of ideal. I have a 
100Mb cable modem connection for the whole house, with wifi 
of course. Oh, what a burden! First world problems...

Anyway, social/economic issues aside, it's my desire to do 
quirky and esoteric things with my computers. One of those 
is to get my z80 online in a somewhat "authentic" way if 
possible, and without adding to the household budget. 
Therefore:

Requirement 1: Use the existing connection to the internet.

Ok, that's fine, I can live with that. I'll be connected via 
a serial port, so I could imagine that I was using a modem. 
And what does a modem do? It connects you to, and allows you 
to use, a remote resource. The only difference, I think, 
will be "how remote is the resource?" In the case of a 
traditional modem, the remote resource might be in the same 
city, or state- an ISP or BBS, for example.

Here's another question: what did the ISP or BBS generally 
provide? That's a tough one. The BBS scene was pretty 
varied; I think I won't be getting that experience *except* 
through telnet/ssh connections to BBSes that are out there 
after I find a solution. I'll be getting more of an ISP 
experience. In the past, I did have an ISP that provided a 
shell account along with the internet... so, I'll pretend 
that I'm my own ISP, and I'll provide a *nix shell. That 
brings be to:

Requirement 2: This is all pretend fun, treat it that way.
Requirement 3: Provide a basic shell environment with 
               internet access.

Are you with me so far? Here's the thing that I *don't* 
want, so it's clear: I don't want to use my z80 computer as 
a dumb terminal to access the full computing power of the 
Pi. I can do that already, it's not what I'm aiming for with 
this project. Heck, I could just connect my VT100/VT52 
terminal directly to the Pi and bypass the z80 SBC 
altogether, right? Nuh uh, not what I'm aiming for. What I 
*do* want is to feel like or simulate "being online" with 
my z80 computer. So:

Requirement 4: Make sure the shell access only provides 
               internet connectivity, and not access to the
               computing resources of the Pi. A limited 
               shell with telnet and ssh out to the 
               internet, and nothing more.

Hope that makes sense, but it's a monologue, so it doesn't 
matter. In any case, what I think I'll get, what I'm aiming 
for here, is the ability to use *truly remote* resources and 
opportunities. That's what I view the internet as, roughly 
speaking.

Oh, I just thought of another thing:

Requirement 5: Have the ability to download items to the z80 

So, maybe I'll need x/y/zmodem programs in addition to 
telnet and ssh? Kermit? I'm not entirely sure, but I'll need 
to figure that out. 

OR... should I basically provide a stub that connects me 
directly to SDF? In other words, when I open the serial port 
it connects me to a getty (or whatever) on the Pi, which in 
turn is configured to automatically provide me with a prompt 
to login to SDF instead of a local login prompt. I think 
that might feel even more authentic; I wouldn't really be 
using the Pi for anything other than a connection to the 
internet, as I'd use a modem. I'll add:

Stretch goal: Instead of basic shell, provide a direct 
              method to login to my remote shell on SDF, 
              therefore having no access to the local 
              resources of the pi.

Voila. I have my next z80 SBC related project all lined up!

*NOTE: I realize that most z80's never saw the ppp/slip
tcp/ip stuff that I was used to with my mid-90s computers.
Even the 8088 that I grew up with had an ethernet card at
one point. Perhaps z80 computers were used for BBS access,
time sharing systems, and the like. I'll still consider a
connection to SDF as quite sufficient for what I want.

[1] gopher://sdf.org:70/0/users/tfurrows/phlog/2018/afn_pcEcosys.txt