Programming

Race conditions can still happen when the server is interrupted while writing to the shared mem. Until the server finishes, clients would view incompletely-updated data. If your data structure is just a "video buffer" this probably won't cause crashing, though you could get the ASCII equivalent of video tearing.

Might UNIX domain sockets work for you? They're not network sockets per-se, local-only, and designed for your problem(among others; things like syslog, mysql, and X11 also use them for local communication.) They're like beefed-up FIFOs. The server creates a special file, probably under /tmp/ or /var/run/, which clients connect to. Unlike fifo's, more than one client can connect simultaneously. The server checks for connections with the accept() system call like a network socket would. Once that succeeds there's a communication channel between the client and the server. The server would fork off a process to deal with this connection and close its own copy afterwards.

There's no easy way beyond this, really. That's what this is there for. If you want to do without you'll just be building your own private version of the same thing.

Thanks for your help...very much appreciated...I'll try to learn some more about domain sockets as I'm not that familiar with the topic.

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one last thing hehe....do u guys have any idea of how I can distribute the same screen among multiple terminals ? I am using ncurses and want to distribute the WINDOW structure to all the connected terminals.

ncurses didn't work that way last time you asked, and continues to not work that way now. Each process will have to be responsible for its own drawing and nobody else's.

It's a variation of a fairly common question actually: "how do I write to 9 files with one fd?" You really can't. Yours is complicated by three layers of other problems though!

do you think it's possible to have a process write the WINDOW to a file which multiple processes read from simultaneously ? I had tried to do this using shared memory by having the window kept in shared memory but each time I accessed the window from the child process I kept getting a segmentation fault. Any ideas ? Thanks for your help and patience btw..thank god for ppl like u!

curses won't treat a file like a terminal and won't be fooled. Besides, whose to say all your clients will be using the same terminal? You need to let your clients do their own drawing. This is because, as stated twice previously, curses does not work that way. A WINDOW structure created in one process won't be valid in another. In fact any pointers and things containing pointers won't be valid when shared. Pointers point to memory local to its process, if they even point to any valid memory in a different process it will be a complete coincidence.

I think you're going to have to give up on sharing terminals with other processes and share data with them instead. Tell them what to draw but let them do their own drawing. (or just redraw everything every frame, and make it more efficient later.) You could keep an 80x25 character array in shared mem, and communicate to your clients what sections they need to redraw, or perhaps just when. I do think you'll need synchronization to accomplish this well.

If you have shared memory, why does the server need to handle the input?

The client process writes and reads shared memory. What else is needed?

fully agree with you.

Reinventing inter-client communication with shared memory is essentially building your own pipes and sockets from scratch. Besides, he said he didn't want to do any synchronization.

Wait, you don't actually agree with him, you're a spammer advertising something.