Just a quick reference of how to work with IPs.

ips.cpp

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

enum {
	/* Maximum length of a string representing an IPv4 address */
	IP4_LEN_MAX = 3 * 4 + 3 + 1
};

int
main(void) {

	// Input IPs in text format
	char *startIP = (char *) "192.168.178.2";
	char *stopIP = (char *) "192.168.178.1";
	printf("start=%s stop=%s\n\n", startIP, stopIP);

	// Convet text to binary format
	uint32_t start, stop;
	inet_pton(AF_INET, startIP, &start);
	inet_pton(AF_INET, stopIP, &stop);
	printf("start=0x%08X stop=0x%08X\n", start, stop);

	// Convert number from network-byte-order (big endian)
	// to host-byte-order (little endian for x86)
	start = ntohl(start);
	stop = ntohl(stop);
	printf("start=0x%08X stop=0x%08X\n", start, stop);

	if (start > stop) { int temp = start; start = stop; stop = temp; }

	// Convert number from host-byte-order (little endian for x86)
	// to network-byte-order (big endian)
	start = ntohl(start);	
	stop = ntohl(stop);
	printf("start=0x%08X 0stop=0x%08X\n\n", start, stop);


	/* Four octets, at most 3 bytes + 3 bytes as delimiters + 1 terminating 0x00 */
	startIP =(char *) calloc(IP4_LEN_MAX, sizeof(char));
	stopIP  =(char *) calloc(IP4_LEN_MAX, sizeof(char));

	// Convet binary to text format
	inet_ntop(AF_INET, &start, startIP, IP4_LEN_MAX * sizeof(*startIP));
	inet_ntop(AF_INET, &stop,  stopIP,  IP4_LEN_MAX * sizeof(*startIP));
	printf("start=%s stop=%s\n", startIP, stopIP);
	free(startIP);

	return 0;
}