利用Magic Packet启动电脑

许多电脑支持从网络唤醒，这样的电脑一般从网卡驱动里选择启用Wake up功能，选择Magic Packet启动即可。

比如，我的Atheros网卡就是支持的：

选好这个之后，再记录下网卡的MAC地址，可以使用getmac命令，或者ipconfig。

然后在同局域网另一台电脑上使用Magic Packet Sender软件发包，即可启动电脑。

Magic Packet的包格式很简单，理论上可以在任意网络封包中打包Magic Packet，不过一般选择UDP或IPX。

Magic Packet的格式是，首先包含六个FF，然后是重复十六次待唤醒电脑的MAC。比如上图的封包，就应该是这样：

FF FF FF FF FF FF 20 12 04 24 13 43 20 12 04 24 13 43 ......

所以，它的编码实现是很简单的，下面附上我自己写的Magic Packet发包程序：

#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 <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> void fill_magic_buf(void *magic_buf, void *mac) { int i; char *ptr; ptr = magic_buf; memset(ptr, 0xFF, 6); ptr += 6; for(i = 0; i < 16; ++i) { memcpy(ptr, mac, 6); ptr += 6; } } void usage(void) { printf("usage...\n"); } int main(int argc, char **argv) { int s; int packet_num = 10; char c; unsigned char mac[6] = {0x00, 0x1A, 0x92, 0xE5, 0x1B, 0xA7}; char dstip[256] = "192.168.9.180"; int port = 9; struct sockaddr_in address; char magic_buf[6 + 6 * 16] = {0}; daemon(0,0); /* run in background */ while((c = getopt(argc, argv, "d:m:p:")) != -1) { switch(c) { case 'd': strcpy(dstip, optarg); break; case 'm': sscanf(optarg, "%x:%x:%x:%x:%x:%x", (unsigned int*)&mac[0], (unsigned int*)&mac[1], (unsigned int*)&mac[2], (unsigned int*)&mac[3], (unsigned int*)&mac[4], (unsigned int*)&mac[5]); break; case 'p': port = atoi(optarg); break; default: usage(); return -1; } } s = socket(AF_INET, SOCK_DGRAM, 0); if (s == -1) { perror("Opening socket"); exit(EXIT_FAILURE); } memset(&address, 0, sizeof(struct sockaddr_in)); address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr(dstip); address.sin_port = htons(port); fill_magic_buf(magic_buf, mac); /* ten packets. TODO: use ping to check whether the destination is on or else. */ while (packet_num-- > 0) { if (sendto(s, magic_buf, sizeof(magic_buf), 0, (struct sockaddr *)&address, sizeof(address)) < 0) { printf("sendto\n"); exit(EXIT_FAILURE); } sleep(1); } exit(EXIT_SUCCESS); }