Use magic packet to start your computer

Many computers support wake-up from the network. Generally, these computers choose to enable the wake up function from the NIC Driver and choose magic packet to start.

For example, my atheros Nic supports:

After selecting this, record the MAC address of the NIC. You can use the getmac command or ipconfig.

Then, use the magic packet sender software to send packets on another computer in the same LAN to start the computer.

The packaging format of magic packet is very simple. Theoretically, magic packet can be packed in any network packet, But UDP or IPX is generally used.

The magic packet format is: First, it contains six ff, and then it is repeated for sixteen times to wake up the computer's Mac. For example, the packet should be like this:

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

Therefore, its encoding implementation is very simple. The following is a magic packet package program I wrote:

#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);}

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Note: If the wol function is enabled, the Mac and IP addresses of the NIC are in the active state. That is, the computer is active from the perspective of other machines on the LAN.