Question

I want to have a web page (written in php because it’s what i know) that displays an input value. I want that value to be passed to a c programa that’s already running.

I though of using sockets to communicate between both process, but how do I manage to do that? how can I use fsockopen to connect to a local socket.

Answer 1

Some simple solutions I can think of are:

Redis

You could use redis as your ipc using hiredis as your c client library. I never used hiredis library before but did it just now for you to test and the library is really good. I could have known it because redis is the best piece of C code I know :).

modify example.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "hiredis.h"

int main(void) {
    redisContext *c;
    redisReply *reply;

    c = redisConnect((char*)"127.0.0.1", 6379);
    if (c->err) {
        printf("Connection error: %s\n", c->errstr);
        redisFree(c);
        exit(1);
    }

    /* Blocking pop. */
    reply = redisCommand(c, "BLPOP php 0");
    if (reply->type == REDIS_REPLY_ARRAY) {
        if (reply->elements == 2) {
            printf("%s\n", reply->element[1]->str);
        }
    }
    freeReplyObject(reply);
    redisFree(c);
    return 0;
}

Compile and run example:

make
./hiredis-example

from ./redis-cli:

from another tab start start redis-cli(for prototyping) and issue the following command. You should replace this with predis as php client library, but that is going to be very easy:

lpush php "Hello from PHP"

Inside running hiredis-example:

You should see the message “Hello from PHP”. Easy as pie if you ask me :).

Named pipes

You could use a named pipes.

Sockets

You could read the Beej’s Guide to Network Programming Using Internet Sockets. In my opinion this is a very good read.