1 #include <sys/types.h>
2 #include <sys/socket.h>
3
4 #include <arpa/inet.h>
5 #include <netinet/in.h>
6
7 #include <err.h>
8 #include <stdio.h>
9 #include <stdint.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <unistd.h>
13
14 static void
usage(const char * cmd)15 usage(const char *cmd)
16 {
17 fprintf(stderr, "%s -4 ip4 -p port\n", cmd);
18 exit(1);
19 }
20
21 int
main(int argc,char * argv[])22 main(int argc, char *argv[])
23 {
24 struct sockaddr_in in, in2;
25 int s, opt, n;
26 uint8_t buf[18];
27
28 memset(&in, 0, sizeof(in));
29 in.sin_family = AF_INET;
30
31 while ((opt = getopt(argc, argv, "4:p:")) != -1) {
32 switch (opt) {
33 case '4':
34 if (inet_pton(AF_INET, optarg, &in.sin_addr) <= 0)
35 usage(argv[0]);
36 break;
37
38 case 'p':
39 in.sin_port = strtol(optarg, NULL, 10);
40 in.sin_port = htons(in.sin_port);
41 break;
42
43 default:
44 usage(argv[0]);
45 }
46 }
47
48 if (in.sin_addr.s_addr == INADDR_ANY || in.sin_port == 0)
49 usage(argv[0]);
50
51 s = socket(AF_INET, SOCK_DGRAM, 0);
52 if (s < 0)
53 err(2, "socket failed");
54
55 if (connect(s, (const struct sockaddr *)&in, sizeof(in)) < 0)
56 err(2, "connect failed");
57
58 memset(&in2, 0, sizeof(in2));
59 in2.sin_family = AF_UNSPEC;
60 connect(s, (const struct sockaddr *)&in2, sizeof(in2));
61
62 n = sendto(s, buf, sizeof(buf), 0,
63 (const struct sockaddr *)&in, sizeof(in));
64 if (n < 0)
65 err(2, "sendto failed");
66 else if (n != (int)sizeof(buf))
67 errx(2, "sendto truncated data %d", n);
68
69 n = read(s, buf, sizeof(buf));
70 if (n < 0)
71 err(2, "read failed");
72 printf("read %d, done\n", n);
73
74 exit(0);
75 }
76