1 #include <stdio.h>

2 #include <stdlib.h>

3 #include <string.h>

4 #include <unistd.h>

5 #include <sys/types.h>

6 #include <sys/socket.h>

7 #include <arpa/inet.h>

8 #include <sys/time.h>

9 #include <sys/select.h>

10

11 #define MAGIC 0x6d0f

12 #define DISCOVER 1

13 #define DREPLY 2

14

15 struct message {

16 int magic;

17 int type;

18 char data[24];

19 };

20

21 int discover(struct sockaddr_in *client_sa);

22

23 int opt_dport = 0x6d0f; /* discover broadcast port */

24 unsigned int opt_timeout = 5000; /* 10 sec discovery timeout */

25

26 int main(int argc, char **argv)

27 {

28 }

29

30 int discover(struct sockaddr_in *client_sa)

31 {

32 int s, true = 1;

33 struct sockaddr_in sa;

34 unsigned int timeout = opt_timeout;

35 struct message msg;

36 struct timeval tv, tv_timeout;

37

38 if((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1) {

39 perror("failed to create discover datagram socket");

40 return -1;

41 }

42 setsockopt(s, SOL_SOCKET, SO_BROADCAST, &true, sizeof true);

43

44 memset(&sa, 0, sizeof sa);

45 sa.sin_family = AF_INET;

46 sa.sin_port = htons(opt_dport);

47 sa.sin_addr.s_addr = htonl(INADDR_ANY);

48

49 if(bind(s, (struct sockaddr*)&sa, sizeof sa) == -1) {

50 perror("failed to bind datagram socket");

51 close(s);

52 return -1;

53 }

54

55 do {

56 msg.magic = MAGIC;

57 msg.type = DISCOVER;

58

59 memset(&sa, 0, sizeof sa);

60 sa.sin_family = AF_INET;

61 sa.sin_port = htons(opt_dport);

62 sa.sin_addr.s_addr = 0xffffffff;

63

64 if(sendto(s, &msg, sizeof msg, 0, (struct sockaddr*)&sa, sizeof sa) == -1) {

65 perror("failed to send discovery bcast dgram");

66 close(s);

67 return -1;

68 }

69 } while(0);

70

71 close(s);

72 return 0;

73 }