| #include <sys/socket.h> |
| #include <netinet/in.h> |
| #include <netinet/tcp.h> |
| #include <arpa/inet.h> |
| #include <inttypes.h> |
| #include <errno.h> |
| #include <stdio.h> |
| #include <unistd.h> |
| |
| int main(int argc, char *argv[]) { |
| int s; |
| struct sockaddr_storage sa; |
| socklen_t salen; |
| uint16_t port; |
| |
| if ((s = socket(PF_INET6, SOCK_STREAM, 0)) < 0) { |
| if (errno == EAFNOSUPPORT) |
| s = socket(PF_INET, SOCK_STREAM, 0); |
| |
| if (s < 0) { |
| perror("socket()"); |
| return 1; |
| } |
| } |
| |
| if (listen(s, 2) < 0) { |
| perror("listen()"); |
| return 2; |
| } |
| |
| salen = sizeof(sa); |
| if (getsockname(s, (struct sockaddr*) &sa, &salen) < 0) { |
| perror("getsockname()"); |
| return 3; |
| } |
| |
| if (((struct sockaddr*) &sa)->sa_family == AF_INET) |
| port = ((struct sockaddr_in*) &sa)->sin_port; |
| else |
| port = ((struct sockaddr_in6*) &sa)->sin6_port; |
| |
| printf("Selected port number %u\n", ntohs(port)); |
| |
| /* ... hic sunt leones ... */ |
| |
| sleep(60); |
| |
| return 0; |
| } |