#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>

#define PORT 845
#define MAX_CONN 5


int daemonize()
{
	pid_t	pid, sid;

	pid = fork();
	if(pid < 0)
		exit(EXIT_FAILURE);

	if(pid > 0) {
		printf("\nDaemon started at pid: %d\n", pid);
		exit(EXIT_SUCCESS);
	}
	umask(0);
	
	sid = setsid();
	if(sid < 0) {
		printf("Failed to set seesion id.\n");
		exit(EXIT_FAILURE);
	}
	
	close(STDIN_FILENO);
	close(STDOUT_FILENO);
	close(STDERR_FILENO);
	
	return pid;
}

void sigchild_handle(int i)
{
	while(waitpid(-1, NULL, WNOHANG) > 0);
}

int main(int argc, char **argv)
{
	int			sockfd, sessfd, retval;
	int 			i, val = 1;
	struct sockaddr_in	serv_addr, conn_addr;
	socklen_t		sin_size;
	struct sigaction	sa;
	char			send_buf[256], recv_buf[256];

	retval = daemonize();
	if(retval) { 			/* This should never happen, but... */
		printf("Daemonize failed: %d\n", retval);
		exit(EXIT_FAILURE);
	}

	if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)
        	exit(EXIT_FAILURE);
    	
	if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,&val, sizeof(int)) == -1)
		exit(EXIT_FAILURE);
	
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(PORT);
	serv_addr.sin_addr.s_addr = INADDR_ANY;
	memset(&(serv_addr.sin_zero), '\0', 8);

	if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1)
		exit(EXIT_FAILURE);
	
	if (listen(sockfd, MAX_CONN) == -1)
		exit(EXIT_FAILURE);
	
	sa.sa_handler = sigchild_handle;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCHLD, &sa, NULL) == -1)
        	exit(EXIT_FAILURE);

	/* Phew.  Now we're set up!  Let's do the BIG LOOP! */
	
	while(1) {
		
		sin_size = sizeof(struct sockaddr_in);

		if((sessfd = accept(sockfd, (struct sockaddr *)&conn_addr, &sin_size)) == -1)
			exit(EXIT_FAILURE);
		
		if(!fork()) {
			close(sockfd);
			strcpy(send_buf, "Service Name: ");
			send(sessfd, send_buf, strlen(send_buf), 0);
			recv(sessfd, recv_buf, sizeof(recv_buf), 0);
			strcpy(send_buf, "The service you have requested does not exist on this server, error: ");
			strcat(send_buf, recv_buf);
			send(sessfd, send_buf, strlen(send_buf), 0);
			close(sessfd);
			return 0;
		}
		close(sessfd);
	}
	return 0;
}