19wintersp's comments

MARLEY seems to have more in common with KASETA, even though they have different file endings. `AA::` and `BB::`, a large section of `- - -`... and second byte alternation are present near the start of both, as well as the large section of `1`s (assuming this is all in ASCII). Are they all the same file format?

I'm guessing they're all from a word processor at this point - Text602 is a shot in the dark from a vague link on Wikipedia - and I think the file is structured as pairs of bytes, with the first being some data, and the latter being a presentation attribute. For example, I'm guessing from LINEN that `0x06` indicates superscript.

It's "magic", yes. Replit is not for you to mess around with the VNC or anything, that directly defeats its purpose. Replit is not a framework for building a Replit-like system. Replit is effectively just a way for you to save and interact with VMs in the cloud from your browser.

The whole point of this demo is "someone ran VICE on Replit". The VNC is completely besides the point.

Again, let me stress this: xterm.js is providing the console only. Any visual things, including the x64 window, are provided by the VNC connection, which is completely independent of the xterm console.

1. It is an emulator program that has nothing to do with Replit, it is just being run on Replit.

2. To repeat, the VNC program is not running the retro OS, that is the emulator. The emulator is a program which runs on Linux and opens a window to show you the emulated computer's screen. That program is being run on Replit, and you can see the screen because it is being connected to you via VNC. I can't answer for why it's slow; that could be the repl, the VNC connection or the emulator itself.

3. The VNC client is no-vnc (I think) and is encrypted. If there's a bug with it, report it to Replit.

The whole point of Replit is to abstract all of this; at the end of the day it just gives you a browser interface to a VM in the cloud, with a filesystem you can save to between sessions. You just interact with it as you would any other Linux system, as all of these layers of abstraction you don't have access to are just providing this simple interface. You don't even interact with anything outside, so there is absolutely no point in using it when developing anything other than for the Replit system itself.

1. I'm assuming by "the box" you mean the VM. It gets started for you when you run the repl as a user who does not own it, and it will run a command specified in a configuration file (see https://docs.replit.com/programming-ide/configuring-run-butt...) and send you the output, as well as let you provide input. It will also detect the run program doing things such as starting to listen on ports (which will be forwarded to a public URL (only under certain circumstances (this is a bit confusing and a bit broken (I don't fully understand it)))) or opening X sessions, in which case it will start the VNC connection to your client. Other than that, it's fairly simple; just think of it as a VM running in the cloud, connected to you, and running a program specified by the creator.

2. I'm almost 100% sure that it's xterm.js, though to be clear I say that it is used to render the console that you briefly see whilst it is compiling. The desktop - which is how you are seeing the emulator window - is provided by a VNC client.

3. Replit is largely closed-source, unfortunately. The protocol is just the way in which the Replit IDE and client communicate with the VMs on the backend. I've summarised some of the behaviour of the backend in my other comment, most of which is known through messages or posts from their engineers. By that summary, it means that the protocol is Protobuf-based. If you want to see a sample of the stuff it sends to the server, you can open a repl you own, append `?debug=1` to the end of the URL, and click the alien logo on the left.

If you want a fuller explanation, I'll just ramble about some random bits. Replit will let you create an account, with which you can create "repls": on their own, they are the "disk images" I mentioned; they store files and a few other bits on Replit's servers. You can open this repl if you own it, and edit it in the in-browser (Monaco-based) IDE. Because you own it, Replit will spin up a VM on its servers to handle your session. Your changes sync in real-time with the permanent files in the repl, as well as the live (and ephemeral) filesystem of the VM. All of this happens over the WebSocket-based protocol I mentioned. What you're seeing with this post's link is a repl owned by someone else; in such a case, you see the "Spotlight View", which is read-only. You can fork it to create your own copy of the repl, which you can edit. The list of files is a read-only view of the repl's files. When you run it, it'll spin up a VM similarly to how it does for you with the IDE. The VM I've been mentioning is a restricted Docker container running on some GCP container instances, managed by Replit. It runs Ubuntu 20.04 LTS (I think) if that's what you want to know. The desktop you see when you run this post's link is a VNC connection to a Fluxbox desktop on the VM. The console is sent from the VM to your browser (again, all of this is over that WebSocket protocol) and rendered by xterm.js. Overall it's a bit of a messy system, and there's quite a few other things not mentioned; they'll occasionally talk about this on the blog (https://blog.replit.com/). If you want something more specific explaining, I'll probably do a better job at that.

1. The information gets from the VM to you through a custom WebSocket protocol called Goval (you can see the JS client at https://github.com/replit/crosis). It can do editing, console I/O, VNC, configuration of the image, etc.

2. The console is rendered with xterm.js, the desktop is a VNC client.

3. Not sure what you mean

It's a read-only "IDE" of sorts; it's effectively a disk image stored in the cloud, which when run will create a VM and send the output back to you. If you create an account, you can fork that repl to create your own editable version of it, and access the full IDE.