Question

i have never done embedded (i dont know if thats what you call this) programming and know nothing about it. my question:

1. is it possible to have two devices sharing a wireless connection (no internet, just between themselves, perhaps bluetooth, but i dont know what ever is best) ?

2. is it possible to have one editing a file and the other person editing the same file and they can see changes in real time? sort of like google docs?

3. does this exist already?

4. what can i do to get started regarding this kind of programming?

to clarify:

i want two people with iphones or any other hand held device, to be able to edit a text file at the same time and see each other’s changes in real-time. how do i do this?

Answer 1

1. Two devices can share a connection like this. It’s done all the time. There are many many protocols for this. Weather or not it is wired or wireless or uses the Internet doesn’t really matter for 90% of this.

2. This is sort of doable, but not really. You really have a race condition when two people are editing at the same time. This is generally avoidable by locking out small parts of the document at from all but one editor at a time (like only one person being able to edit one cell of a spreadsheet at a time), but this has problems too (like of the one active editor is taking way too long — this is a problem seen in many source version control systems too).

3. 1 already exists in many many forms. 2 sort of exists in many forms, but the problems I mentioned are impossible to completely overcome.

4. The way you asked this question leads me to believe that you are very far from being able to do this. In addition, you didn’t tell us anything about what you do know how to do. Can you write a simple text editor for an iPhone (or anything else)? Simple text editors from scratch that aren’t crappy aren’t easy to write.

What you need to do, if you really want to do this, is to come up with a protocol for the two (or more) devices to talk to each other in. To do this it is probably best if you figure out what type of communication is available between the devices and which of those you will use and what features it does not provide that you will need on top.

You could try to send patches of the file (or something similar) between the two devices as edits are made, but then you’ll have to decide what to do in the event of a collision (edits near the same place).

Alternately you could have the two devices exchange permission to make edits (like in token ring networks).

You still have a problem if the two devices lose communication with each other during the editing of the file, though. With the token ring type setup you stand the possibility of losing the token and neither being able to automatically recover easily. Whatever you do you end up with the problem of the two ending up with different ideas of the file’s contents.