wake.c in git
WAKE(1)                 FreeBSD General Commands Manual                WAKE(1)

NAME
     wake – wake-on-LAN

SYNOPSIS
     wake

DESCRIPTION
     wake broadcasts a wake-on-LAN packet for ‘04:7D:7B:D5:6A:53’.

FreeBSD 12.0-RELEASE-p3        September 7, 2018       FreeBSD 12.0-RELEASE-p3
/* Copyright (C) 2017  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <sys/types.h>

#include <err.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sysexits.h>

typedef unsigned char byte;

#define MAC 0x04, 0x7D, 0x7B, 0xD5, 0x6A, 0x53
static const byte Payload[102] = {
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	MAC, MAC, MAC, MAC, MAC, MAC, MAC, MAC,
	MAC, MAC, MAC, MAC, MAC, MAC, MAC, MAC,
};

int main() {
	int sock = socket(PF_INET, SOCK_DGRAM, 0);
	if (sock < 0) err(EX_OSERR, "socket");

	int on = 1;
	int error = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
	if (error) err(EX_OSERR, "setsockopt");

	struct sockaddr_in addr = {
		.sin_family = AF_INET,
		.sin_port = 9,
		.sin_addr.s_addr = INADDR_BROADCAST,
	};
	ssize_t size = sendto(
		sock, Payload, sizeof(Payload), 0,
		(struct sockaddr *)&addr, sizeof(addr)
	);
	if (size < 0) err(EX_IOERR, "sendto");

	return EX_OK;
}