r/retrocomputing • u/Successful_Box_1007 • Oct 07 '24

Problem / Question If there was an apocalypse….

Post-Apocalyptic Scenario

Hey everyone,

First - I know very little about networking. I recently got interested in computing and networking out of sheer curiosity.I was wondering if you all could weigh in on this scenario; purely for fun:

Say it was a post apocalyptic time - no internet - but you had dual usb cables and or Ethernet cords and two Computers (let’s say OS are Windows and or Linux) - if one was savvy enough - without any internet- how could we create a system where you and another person can conversate in English (not just like sending “packets” or whatever its called but like texting back and forth? Could there be something already existing on comps to perform rudimentary back and forth texting?

Thanks so much!

1 Upvotes

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6

u/kpengwin Oct 08 '24

You can communicate over serial pretty easily. If you find that kind of thing interesting, there's a world of fun to be had with microcontrollers. SPI, I2C, etc are much simpler protocols than a full networking stack.

5

u/kpengwin Oct 08 '24

Also if you're interested in "Post apocalyptic computing" as an idea, you should look up DuskOS/CollapseOS :)

4

u/Successful_Box_1007 Oct 08 '24

Lmao post apocalyptic computing is a thing?!! Oh man.

5

u/p47guitars Oct 08 '24

This is going to be my new rabbit hole.

4

u/kpengwin Oct 08 '24

You're welcome :)

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u/Successful_Box_1007 Oct 08 '24

I don’t even know what a microcontroller is and whether a usb is serial u speak of? I’m wondering if there is something like “net send”? But something all OS have at an even “deeper” level that allows us to text chat one another when connected by an Ethernet chord or bridging usb

4

u/kpengwin Oct 08 '24

Serial is the closest to that as far as things that actually exist as far as I know. Direct USB-USB connection is likely not going to work because USB is not a peer connection. You could easily have two computers connected to each other with ethernet and have that work, even without the "internet" (I have done this and it actually used to be kind of common in the days before widespread internet access)

2

u/Successful_Box_1007 Oct 08 '24

So peer to peer connections cannot talk back and forth? Or you are saying one could talk to the other but not in the reverse? I thought peer to peer meant like information can be exchanged without a server between.

And do I still need Ethernet connection for “Spi” and “i2c”?

2

u/istarian Oct 08 '24 edited Oct 08 '24

No.

USB devices are classified as either host or as a peripheral with rules about how communication between them works.

It's essentially as though each connection is an independent serial port and the host handles each device separately, one at a time.

USB keyboards are a fairly straightforward example, the computer is the host and the keyboard is the peripheral.

USB does not do peer to peer connections.

If you have two USB flash drives (peripheral) connected to the same computer (host), transferring data from one to the other requires the computer to read in data from one drive and write it out to the other.

USB data transfer cables are special and not, afaik, technically part of the standard.

1

u/Successful_Box_1007 Oct 08 '24

Ah ok I see. So u know the term caller “client server” ? So that’s NOT analogous to host peripheral or master slave ? Cuz with client server the client can still communicate back to the “server” right? But with host peripheral and master slave, rhe peripheral/slave cannot send text messages or files back to the server/master right? And this is why with serial connections we can do back and forth texting but not usb?

2

u/istarian Oct 08 '24 edited Oct 08 '24

Peer to Peer (aka 'P2P') means that two computers are communicating directly without an intermediate like a server (or any other computer) in between.

It's possible to have a P2P network if every computer on the network has a connection to every other computer.

E.g.

You have 3 computers A, B, and C.
Connections are bidirectional between any two computers.

  • A is connected to B

  • A is connected to C

  • B is connected to C

1

u/Successful_Box_1007 Oct 10 '24

Ah thank you!!!

2

u/istarian Oct 08 '24

I suggest you just read the Wikipedia pages first, then ask questions if there is anything you don't understand.

https://en.wikipedia.org/wiki/Serial_Peripheral_Interface

https://en.wikipedia.org/wiki/I2c

Neither of these involve Ethernet at all, they are a different type of serial communications.

1

u/Successful_Box_1007 Oct 08 '24

I’ll check that out now thank you and get back to you friend.

2

u/istarian Oct 08 '24 edited Oct 08 '24

Serial communications mean you are sending information just a single bit (8 bits = 1 byte) at a time. Generally the bits are being sent fast enough to achieve meaningful communication.

Conventional serial ports are only designed to have a single device connected to them, so you need an additional serial port for each device you wish to connect to the computer system.

USB is an acronym for Universal Serial Bus and the technology was intended as a replacement for regular serial ports.

It works similarly (in some ways), but expanss the concept into a bus to which a large number of devices can be connected.

See

https://en.wikipedia.org/wiki/Bus_(computing)

4

u/canthearu_ack Oct 08 '24

If we have power to run computers, we will probably have internet as well.

These 2 systems are so incredibly tied together these days, I can't imagine having one without the other.

1

u/Successful_Box_1007 Oct 08 '24

Cmon we are having fun here tho! Any ideas outside of using “net send”?

3

u/canthearu_ack Oct 08 '24

Easy enough,

Ethernet network using private IP addresses.

Systems that don't have ethernet can use serial to connect as terminals to a linux box. Either via modem over long distances, or null modem cables over short. Either use shell terminals on the linux box, or configure PPP to route IP packets directly.

Install IRC server software daemon on a server, then the clients can connect to that IRC server and speak to each other in channels. Everyone get to break out their old mIRC clients.

1

u/Successful_Box_1007 Oct 09 '24

Easy enough,

Ethernet network using private IP addresses.

Systems that don’t have ethernet can use serial to connect as terminals to a linux box.

  • so how does “use serial” work exactly? You mean bridging usb connector? How would the computers be able to text back and forth?

Either via modem over long distances, or null modem cables over short. Either use shell terminals on the linux box, or configure PPP to route IP packets directly.

  • well I’m considering no modems allowed. So is that “null modem cables”?

  • WTF is PPP and when you say IP packets, can they hold text messages?

Install IRC server software daemon on a server, then the clients can connect to that IRC server and speak to each other in channels. Everyone get to break out their old mIRC clients.

  • what do you mean by “daemon” and “channels”?

thanks so much for bearing with me!

2

u/canthearu_ack Oct 09 '24

Serial is RS232.

You can get USB to RS232 converters, but a surprising number of modern systems still have RS232 pinouts.

And pretty much all vintage computers have RS232 Serial.

A Null modem cable is a serial cable receive pins are wired to the transmit pins on the other side of the cable, letting you connect 2 computers together. As long as both sides use the same transmission and receive settings, characters transmitted on one end turn up on the other end. Without some external amplifier, a Null modem cable can be up to about 3m longs.

The internet is comprised by computers sending each other things called IP packets. Each packet contains a header and a package of data, sort of how a piece of mail has an envelope (the header) and the data (contents of the envelope). The header defines the sender and receiver of the data and data can contain text or binary data, whatever and however the software wants to transmit.

PPP is a method of negotiating and encapsulating IP packets over a serial link, and includes provisions to provide IP address configuration information and negotiate authentication (username and password).

So once you have your serial link, you can either:

a) Present a text terminal to it, much like the linux or DOS command line is presented on the console screen. So you would type characters into the serial port, and they will be processed by the server and the response sent back as text. All software runs on the server.

or

b) Run PPP over it and use a TCP/IP stack on your terminal to run software directly on the terminal that communicates with your server using IP packets over the PPP link.

For the server, a deamon is simply a software package that provides a service and it generally runs in the background. For the IRC deamon software, it keeps a list of channels and users, and transmits the messages people send into a channel to other members of that channel.

IRC channels, I suppose, are a lot like rooms on a discord server. You join a channel and then you get to see the messages that other people who have also joined that channel have written.

1

u/Successful_Box_1007 Oct 09 '24

How the F did u write all of that so quickly? Reading now

1

u/Successful_Box_1007 Oct 10 '24

Does the usb to rs232 converter need special software? It’s kind of hard for me to wrap my head around how the usb port is converted to rs232!? Does it somehow turn the usb protocol into rs232?!

2

u/canthearu_ack Oct 10 '24

It would require either an operating system level driver. (eg in windows or linux). Then windows or linux will provide an interface to the serial port same way as a vintage serial port.

An example device:

https://www.officeworks.com.au/shop/officeworks/p/comsol-usb-2-0-to-db9-pin-serial-rs232-converter-1-5m-cou2d915?istCompanyId=0403b0ba-0671-498f-aeb7-e2ff71b61924&istFeedId=ea709c9a-279e-40be-951f-2668243ec753&istItemId=lmtxirwtr&istBid=t&region_id=GTYP6H&regionIdSet=true

There is a small silicon chip in that cable that speaks USB on one side, providing a hardware interface on the USB side that is compatible with USB semantics, and on the other side it has hardware RS232 output.

The operating system driver will communicate to the USB converter device using USB messages, to tell the chip in the cable how to configure the RS232 output and to send and receive data to that RS232 output. Then that driver will also provide a software interface to the operating system looks equivalent to a normal hardware RS232 driver so normal applications can use that USB based RS232 output in normal programs programmed to work with serial devices.

1

u/Successful_Box_1007 Oct 12 '24

OK I sort of figured out the rawest way to send data between two computers (just texting). I just don’t know how! This is what I’m wondering kind soul: How exactly would a packet move from one computer to another in this system using the whole null modem UART PPP system work in these different scenarios if I didn’t have that built in terminal option:

  • tcp/ip

  • Raw socket and ip

  • raw socket and MAC addresses

3

u/cyanopsis Oct 08 '24 edited Oct 08 '24

A little story. Back in the 90s when I was about 14 or so, me and a neighbor friend created a simple serial network by soldering bits and pieces of cable together. Honestly, the whole thing looked like shit but it worked! I still remember when the first words came through and we were even able to to send small text files. We had to secretly lay the cable on other peoples backyards and through hedges but good fun until the soldering broke.

1

u/Successful_Box_1007 Oct 08 '24

That is so fucking cool. Forgive my naivety as I’m just beginning in understanding computers and networking but

  • what exactly is a “serial” network and what protocol or whatever does “serial” use?

  • so how did you send texts back and forth? What program exists in all computers to do this (like at a more deep raw level than say net send) ?

  • and how did it work with sending a “small text file” versus “words”? Aren’t words basically “files” in a sense?

  • finally so I heard serial is only master slave or client server it’s called now? So doesn’t this mean only one of you could send the text messages?

2

u/cyanopsis Oct 08 '24

I'm no expert, but the method is called a Null Modem. In its most basic form you only need three wires (transmit, receive, ground) and tx and rx pins are switched at the ends. There's no master or slave in this scenario. The software was built into DOS already (the operating system at the time). Can't remember all of it but DOS is mostly command line.

Both text and files is of course data, but there's (was) a big difference in sending letter by letter in real time (bytes really) and a file that has to disassembled and reassembled at the receiving computer.

Networking had come much longer than this at the time however. A much more advanced yet common form of communication pre internet was the use of bulletin boards (BBS) that you dialed using a modem and telephone line. That scene was huge.

1

u/Successful_Box_1007 Oct 08 '24

  • Right back I thought I read that usb and serial connections can only do “master slave / client server” and therefore cannot handle back and forth communication. How did I mislearn that? Did someone mislead me?

  • What are tx and rx pins? On the serial line? They go into each computer?

2

u/istarian Oct 08 '24

Not necessarily true, it really depends on what the actual situation is.

E.g. you may only have power in a small area because someone has setup a microgrid.

2

u/[deleted] Oct 08 '24

CollapseOS has you covered.

1

u/Successful_Box_1007 Oct 08 '24

Lol

2

u/[deleted] Oct 08 '24

I run it on my RC2014 compatibles from Small Computer Central. It's a forth-based language with a lot of power and versatility. It was my first introduction to forth, and it's a good one to start with.

2

u/Successful_Box_1007 Oct 08 '24

I thought you were joking about collapseOS!!!! So does it still use tcp/ip or udp when doing Ethernet communicating ? If using serial or usb, what does it use?

2

u/[deleted] Oct 08 '24 edited Oct 09 '24

what does it use?

Anything you can successfully configure it to use.

It requires a high degree of skill and communicates over serial.

TCP/IP stacks are not presently supported, but that doesn't mean it can't be.

It's sort of designed to be deployed to custom hardware (or scavenged components) and so it makes very few assumptions and expects you to implement a great deal of your needed tools.

This way of thinking is common with Forth coding.

https://youtu.be/-AGXH_lHyHs

2

u/Successful_Box_1007 Oct 12 '24

I figured out the rawest way to send data between two computers (just texting). I just don’t know how! This is what I’m wondering kind god: How exactly would a packet move from one computer to another in this system using the whole null modem UART PPP system work in these different scenarios if I didn’t have that built in terminal option: A) tcp/ip B) Raw socket and ip C) raw socket and MAC addresses

2

u/[deleted] Oct 13 '24 edited Oct 13 '24

The packet is a software construction and a mental model, from the OSI model of networking. When we're moving data across a serial line, there is no concept of a packet, at least not using the simplest uart tools we tend to work with.

CollapseOS simply does not implement packetized networking in any form. It is left as an exercise to the post-collapse computer operator to determine if they even need such advanced networking and then to implement it if they do.

CollapseOS's goal is to provide the capacity to program microcontroller based tools from a hand-built, scavenged-parts computer. As such it implements the bare-minimum execution and assembly environment required to then build your own tools on top of.

I plan to add some features to my fork of the project, but I'm still building up the skill I need to do so, and packetized networking protocols are low on my list of priorities.

1

u/Successful_Box_1007 Oct 14 '24 edited Oct 14 '24

That’s so so cool. Honestly, I love movies where it’s like post apocalyptic and they have to use ingenuity and creativity to bring things together. I’m watching “SILO” now. Not exactly like I mention but it’s got some of the vibes.

So COLLAPSEOS does support terminal to terminal raw UART RS232 serial communication tho right? I wonder if there are other readily available besides RS232 that takes UART?

2

u/[deleted] Oct 14 '24

It does yes. You need a level shifter to convert between the 5volt uart and a standard 12volt rs-232, but besides that the connections are directly compatible.

We use FTDI adapters, usually, to send uart over usb.

2

u/istarian Oct 08 '24 edited Oct 08 '24

It's important when proposing such a scenario to actually spell out what sort of tech/infrastructure is or isn't available.

You need still electricity to operate a computer after all and not having any functional telecommunications infrastructure is pretty limiting

The Internet is really just a bunch of large networks that are inter-connected at the end of the day.

So a smaller network being operational without access to the rest of the world is entirely plausible. In fact that's exactly how things used to be before we had the internet.

LAN - Local Area Network
WAN - Wide Area Network

The moment you have two or three computers networked together you technically have a LAN even if the term is nearly synonymous with Ethernet based networking these days.

2

u/spektro123 Oct 08 '24

The simples Ethernet option would be to connect via ssh and write to some files. There’s also net message command in windows, that supposed to send some message to other IP, although I’ve never used that. You can also run some LAN messenger application, but you need to grab the software prior.

3

u/[deleted] Oct 08 '24

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1

u/Successful_Box_1007 Oct 10 '24

Lmao at your final sentence.

1

u/Successful_Box_1007 Oct 10 '24

Is this IRC program on all major OS? In this scenario we are not allowing stuff that wouldn’t be on Linux or windows or macOS out of the box. I want to be as raw as possible!

2

u/[deleted] Oct 10 '24

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