Tiny HTTP server to respond OK on port 9000 - handy for health checks on embedded boxes!

gistfile1.txt

/**
  * Based on http://tinyhack.com/2014/03/12/implementing-a-web-server-in-a-single-printf-call/
  */

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<signal.h>
#include<fcntl.h>

int main(int argc, char *argv[])
{
    int countforks = 0;
    int waitint;
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);

    // If we don't do SO_REUSEADDR, the app fails to start sometime from connections
    // of the last instance that are still around and not yet timed out.
    int reuseaddr = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(reuseaddr));

    struct sockaddr_in serv_addr;
    bzero((char *)&serv_addr, sizeof(serv_addr));
        serv_addr.sin_family = AF_INET;
        serv_addr.sin_addr.s_addr = INADDR_ANY;
        serv_addr.sin_port = htons(9000);
    bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
    listen(sockfd, 5);

    while (1) {
        int cfd  = accept(sockfd, 0, 0);
        char *s = "HTTP/1.0 200\r\nContent-type:text/plain\r\n\r\nHello world!\r\n";

        countforks++;
        if (fork()==0) {
            write(cfd, s, strlen(s));
            shutdown(cfd, SHUT_RDWR);
            close(cfd);
            exit(0);
        } else {
           // because we listen in the main process the socket ends up open in both the child
           // and the parent. We need to close it in the parent to prevent socket leakage.
           close(cfd);

           // We need to waitpid for all child processes to stop us having zombies piling up
           int i; for (i=0; i<=countforks; i++) {
             if (waitpid(-1, &waitint, WNOHANG)) {
                countforks--;
             }
           }
        }
    }

    return 0;
}