When talking about remote machines, sometimes we mean really remote, beyond the realms of wired networks that can deliver the Internet. In these cases, remote cellular access is often the way to go. Thus far, we’ve explored the hardware and software sides required to control a machine remotely over a cellular connection.
However, things can and do go wrong. When that remote machine goes offline, getting someone on location to reboot it can be prohibitively difficult and expensive. For these situations, what you want is some way to kick things back into gear, ideally automatically. What you’re looking for is a watchdog timer!
Maybe you’ve heard of it, maybe you haven’t. Zig is a new programming language that seems to be growing in popularity. Let’s do a quick dive into what it is, why it’s unique, and what sort of things you would use it for. (Ed Note: Other than “for great justice“, naturally.)
So let’s talk Zig. In a broad sense, Zig is really trying to provide some of the safety of Rust with the simplicity and ease of C. It touts a few core features such as:
We’ve all experienced that magic moment when, after countless frustrating hours of experimentation and racking your brain, the object of our attention starts working. The 3D printer finally produces good output. The hacked up laptop finally boots. The car engine finally purrs. The question is, do we know why it started working?
This is more important than you might think. Knowing the answer lets you confirm that the core problem was solved, otherwise you may have just fixed a symptom. And lack of understanding means fixing one problem may just create another.
The solution is to adopt a methodical troubleshooting method. We’re talking about a structured problem solving technique that when used properly can help us solve a problem at its core without leaving any loose ends. Such methodology will also leave you knowing why any solution did or didn’t work in the end, and will give you reproducible results.
A thermal camera is a tool I have been wanting to add to my workbench for quite a while, so when I learned about the tCam-Mini, a wireless thermal camera by Dan Julio, I placed an order. A thermal imager is a camera whose images represent temperatures, making it easy to see things like hot and cold spots, or read the temperature of any point within the camera’s view. The main (and most expensive) component of the tCam-Mini is the Lepton 3.5 sensor, which sits in a socket in the middle of the board. The sensor is sold separately, but the campaign made it available as an add-on.
Want to see how evenly a 3D printer’s heat bed is warming up, or check whether a hot plate is actually reflowing PCBs at the optimal temperature? How about just seeing how weird your pets would look if you had heat vision instead of normal eyes? A thermal imager like the tCam-mini is the tool for that, but it’s important to understand exactly how the tCam-mini works. While it may look like a webcam, it does not work like one.
If you follow cybersecurity hacker methods — or just watch Mr. Robot — you probably know that the best way to get someone’s password is to ask for it. Sure, you probably can’t just say “Hi, I’m a bad guy. Can I have your password?” But there are all sorts of tricks you can use like pretending to be in the person’s IT department, someone in management, or by making up a crisis to overcome their better judgement with a sense. But of course, as wise computer people, we are immune to such things, right? We also don’t need those kinds of tricks in our arsenal.
Is that true? It is amazing how many subtle things influence what we think are rational decisions, no matter who we are. Consider going to eat in a restaurant. Simple, right? You look at the menu, pick what you want, and order. No one is influencing you. But they are. According to a BBC article, there’s a whole industry of menu “engineering” that figures out how to get you to order pricey food.
You might not think social engineering for menus is a great skill for us. But maybe your new open source project needs collaborators. Maybe your startup company needs investors. Maybe you’d like someone to look at your resume. Maybe the same tricks that work with diners will work in those cases, too.
You need to package up a bunch of files, send them somewhere, and do something with them at the destination. It isn’t an uncommon scenario. The obvious answer is to create an archive — a zip or tar file, maybe — and include a shell script that you have to tell the user to run after unpacking.
That may be obvious, but it assumes a lot on the part of the remote user. They need to know how to unpack the file and they also need to know to run your magic script of commands after the unpack. However, you can easily create a shell script that contains a file — even an archive of many files — and then retrieve the file and act on it at run time. This is much simpler from the remote user’s point of view. You get one file, you execute it, and you are done.
In theory, this isn’t that hard to do, but there are a lot of details. Shell scripts are not compiled — at least, not typically — so the shell only reads what it needs to do the work. That means if your script is careful to exit, you can add as much “garbage” to the end of it as you like. The shell will never look at it, so it’s possible to store the payload there.
Twitch Plays Pokemon burst onto the then nascent livestreaming scene back in 2014, letting Twitch viewers take command of a Game Boy emulator running Pokemon Red via simple chat commands. Since then, the same concept has been applied to everything under the sun. Other video games, installing Linux, and even trading on the New York Stock Exchange have all been gameified through Twitch chat.
TwitchPlaysPokemon started a craze in crowdsourced control of video games, robots, and just about everything else.
You, thirsty reader, are wondering how you can get a slice of this delicious action. Fear not, for with a bit of ramshackle code, you can let Twitch chat take over pretty much anything in, on, or around your computer.
It’s Just IRC
The great thing about Twitch chat is that it runs on vanilla IRC (Internet Relay Chat). The protocol has been around forever, and libraries exist to make interfacing easy. Just like the original streamer behind Twitch Plays Pokemon, we’re going to use Python because it’s great for fun little experiments like these. With that said, any language will do fine — just apply the same techniques in the relevant syntax.
SimpleTwitchCommander, as I’ve named it on Github, assumes some familiarity with basic Python programming. The code will allow you to take commands from chat in two ways. Commands from chat can be tabulated, and only the one with the most votes executed, or every single command can be acted on directly. Actually getting this code to control your robot, video game, or pet viper is up to you. What we’re doing here is interfacing with Twitch chat and pulling out commands so you can make it do whatever you like. With that said, for this example, we’ve set up the code to parse commands for a simple wheeled robot. Let’s dive in.
