JavaScript back and forth with running program

Question

Problem:

I'm trying to see if I can have a back and forth between a program running on the server-side and JavaScript running on the client-side. All the outputs from the program are sent to JavaScript to be displayed to the user, and all the inputs from the user are sent from JavaScript to the program.

Having JavaScript receive the output and send the input is easily done with AJAX. The problem is that I do not know how to access an already running program on the server.

Attempt:

I tried to use PHP, but ran into some hurdles I couldn't leap over. Now, I can execute a program with PHP without any issue using proc_open. I can hook into the stdin and stdout streams, and I can get output from the program and send it input as well. But I can do this only once.

If the same PHP script is executed(?) again, I end up running the program again. So all I ever get out of multiple executions is whatever the program writes to stdout first, multiple times.

Right now, I use proc_open in the script which is supposed to only take care of input and output because I do not know how to access the stdout and stdin streams of an already running program. The way I see it, I need to maintain the state of my program in execution over multiple executions of the same PHP script; maintain the resource returned by proc_open and the pipes hooked into the stdin and stdout streams.

$_SESSION does NOT work. I cannot use it to maintain resources.

Is there a way to have such a back and forth with a program? Any help is really appreciated.

Answer 1

This sounds like a job for websockets

Try something like http://socketo.me/ or http://code.google.com/p/phpwebsocket/

I've always used Node for this type of thing, but from the above two links and a few others, it looks like there's options for PHP as well.

Answer 2

There may be a more efficient way to do it, but you could get the program to write it's output to a text file, and read the contents of that text file in with php. That way you'd have access to the full stream of data from the running program. There are issues with managing the size of the file, and handling requests from multiple clients, but it's a simple approach that might be good enough for your needs.

Answer 3

You are running the same program again, because it's the way PHP works. In your case client does a HTTP request and runs the script. Second request will run the script again. I'm not sure if continuous interaction is possible, so I would suggest making your script able to handle discrete transactions.

In order to figure different steps of the same "interaction", you will have to save data about previous ones in database. Basically, you need to give some unique hash to every client to identify them in your script, then it will know who does the request and will be able to differ consecutive requests from one user from requests of different users.

If your script is heavy and runs for a long time, consider making two script - one heavy and one for interaction (AJAX will query second one). In this case, second script will fill data into database and heavy script will simply fetch it from there.