ソースコード例：ICMPパケット送受信(ping)

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <time.h>
#include <netdb.h>

static unsigned short ping_checksum(unsigned short *buf, int bufsz) {
	unsigned long sum = 0;

	while(bufsz > 1) {
		sum += *buf;
		buf++;
		bufsz -= 2;
	}
	if(bufsz == 1) {
		sum += *(unsigned char *)buf;
	}
	sum = (sum & 0xffff) + (sum >> 16);
	sum = (sum & 0xffff) + (sum >> 16);
	return ~sum;
}

#define PING_TIMOUT	7

int main(int argc, char *argv[]) {
	static char		buf[ETHER_MAX_LEN];
	int			sock, i, count, size, j, stat, ret;
	int			n, addrlen, maxsiz, alen;
	char			*ptr;
	time_t			t;
	struct icmphdr		hdr;
	struct sockaddr_in	addr, saddr;
	struct icmphdr		*icmphdrptr;
	struct iphdr		*iphdrptr;
	struct timeval		tv;
	struct hostent		*hp;

	size = 56;
	count = 6;
	ret = -1;
	for(i = 1;i < argc;i++) {
		if(argv[i][0] == '-') {
			if((i + 1) >= argc) {
				break;
			} else {
				if(argv[i][1] == 's') {
					size = atoi(argv[i + 1]);
				} else if(argv[i][1] == 'c') {
					count = atoi(argv[i + 1]);
				} else {
					break;
				}
				i++;
			}
		} else {
			if((hp = gethostbyname(argv[i])) == NULL) break;
			bcopy(hp->h_addr_list[0], &(addr.sin_addr), hp->h_length);
			ret = 0;
		}
	}
	if(ret == -1) {
		printf("usage : %s [ -c COUNT -s SIZE ] IPADDR\n", argv[0]);
		return -1;
	}
	maxsiz = 548 - sizeof(struct iphdr) - sizeof(struct icmphdr);
	if(count > maxsiz) count = maxsiz;
	addr.sin_family = AF_INET;
	sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
	if (sock < 0) {
		printf("socket error\n");
		return -1;
	}
	tv.tv_sec = PING_TIMOUT;
	tv.tv_usec = 0;
	setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
	iphdrptr = (struct iphdr *)buf;
	icmphdrptr = (struct icmphdr *)&(buf[sizeof(struct iphdr)]);

	for(i = 0;i < count;i++) {
		memset(&hdr, 0, sizeof(hdr));
		hdr.type = ICMP_ECHO;
		hdr.code = 0;
		hdr.checksum = 0;
		hdr.un.echo.id = htons(100);
		hdr.un.echo.sequence = htons(i + 1);
		memcpy(buf, (char*)&hdr, sizeof(hdr));
		ptr = &(buf[sizeof(hdr)]);
		for(j = 0;j < size;j++) ptr[j] = j + 0x10;
		hdr.checksum = ping_checksum((unsigned short*)buf, sizeof(hdr) + size);
		memcpy(buf, (char*)&hdr, sizeof(hdr));
		t = time(NULL);
		n = sendto(sock, buf, sizeof(hdr) + size, 0, (struct sockaddr *)&addr, sizeof(addr));
		if (n < 1) {
			printf("sendto error.\n");
			break;
		}
		for(;;) {
			if(time(NULL) > t + PING_TIMOUT) {
				printf("recv error.\n");
				break;
			}
			n = recv(sock, buf, sizeof(buf), 0);
			if(n < 1) {
				printf("recv error.\n");
				break;
			} else {
				if(iphdrptr->protocol == IPPROTO_ICMP &&
				   iphdrptr->saddr == addr.sin_addr.s_addr &&
				   hdr.un.echo.id == icmphdrptr->un.echo.id &&
				   hdr.un.echo.sequence == icmphdrptr->un.echo.sequence) {
				   	printf("%d bytes from %s: icmp_seq=%d ttl=%d\n",
				   	  (int)(ntohs(iphdrptr->tot_len) - sizeof(struct iphdr)), 
				   	  inet_ntoa(addr.sin_addr),
				   	  ntohs(hdr.un.echo.sequence), iphdrptr->ttl);
					break;
				}
			}
		}
		fflush(stdout);
		sleep(1);
	}
	close(sock);

	return 0;
}