What is involved in simultaneous editing of a file?

I'm curious about the ability to simultaneously edit files. How it works, when can't it work. For example, if I put any number of files up on a network share (or maybe DropBox) it's usually not possible to collaborate on them with someone else. Let's 开发者_开发技巧say I want to work on a SolidWorks model with someone else. Is it SolidWorks that locks up the file, is it something that needs to be build into the filetype, or a combination of these?

Ultimately I'm thinking of cool things to do with node.js and socket.io and simultaneously messing with files.

Edit: If anyone knows what Google Docs and other online office suites are doing in the background I'd love specific explanations too.

You should look into using some sort of source control software. It seems like that might be the correct technology for what you are describing. I recently started using Visual SVN. It's free, easy and effective.

http://www.visualsvn.com/