Finding Local IP via Socket Creation / getsockname
- by BSchlinker
I need to get the IP address of a system within C++. I followed the logic and advice of another comment on here and created a socket and then utilized getsockname to determine the IP address which the socket is bound to.
However, this doesn't appear to work (code below). I'm receiving an invalid IP address (58.etc) when I should be receiving a 128.etc
Any ideas?
string Routes::systemIP(){
// basic setup
int sockfd;
char str[INET_ADDRSTRLEN];
sockaddr* sa;
socklen_t* sl;
struct addrinfo hints, *servinfo, *p;
int rv;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
if ((rv = getaddrinfo("4.2.2.1", "80", &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return "1";
}
// loop through all the results and make a socket
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("talker: socket");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "talker: failed to bind socket\n");
return "2";
}
// get information on the local IP from the socket we created
getsockname(sockfd, sa, sl);
// convert the sockaddr to a sockaddr_in via casting
struct sockaddr_in *sa_ipv4 = (struct sockaddr_in *)sa;
// get the IP from the sockaddr_in and print it
inet_ntop(AF_INET, &(sa_ipv4->sin_addr.s_addr), str, INET_ADDRSTRLEN);
printf("%s\n", str);
// return the IP
return str;
}
