1 #include <sys/socket.h>
2 #include <netinet/in.h>
3 #include <netinet/tcp.h>
4 #include <arpa/inet.h>
5 #include <inttypes.h>
6 #include <errno.h>
7 #include <stdio.h>
8 #include <unistd.h>
9
main(int argc,char * argv[])10 int main(int argc, char *argv[]) {
11 int s;
12 struct sockaddr_storage sa;
13 socklen_t salen;
14 uint16_t port;
15
16 if ((s = socket(PF_INET6, SOCK_STREAM, 0)) < 0) {
17 if (errno == EAFNOSUPPORT)
18 s = socket(PF_INET, SOCK_STREAM, 0);
19
20 if (s < 0) {
21 perror("socket()");
22 return 1;
23 }
24 }
25
26 if (listen(s, 2) < 0) {
27 perror("listen()");
28 return 2;
29 }
30
31 salen = sizeof(sa);
32 if (getsockname(s, (struct sockaddr*) &sa, &salen) < 0) {
33 perror("getsockname()");
34 return 3;
35 }
36
37 if (((struct sockaddr*) &sa)->sa_family == AF_INET)
38 port = ((struct sockaddr_in*) &sa)->sin_port;
39 else
40 port = ((struct sockaddr_in6*) &sa)->sin6_port;
41
42 printf("Selected port number %u\n", ntohs(port));
43
44 /* ... hic sunt leones ... */
45
46 sleep(60);
47
48 return 0;
49 }
50