inet_ntop always returns the same IP - c

Question

Spending way too much time trying to figure out why inet_ntop is always returning the same IP address of 2.0.19.86 inside of my barebones C UDP socket program.
Here is the code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define SERVERPORT "4950" // the port users will be connecting to
int main(int argc, char *argv[])
{
int sock;
struct addrinfo addr_type, *server_info, *p;
int err;
int numbytes;
if (argc != 3) {
fprintf(stderr,"usage: talker hostname message\n");
exit(1);
}
//Specify type of response we want to git
memset(&addr_type, 0, sizeof addr_type);
addr_type.ai_family = AF_INET; // set to AF_INET to use IPv4
addr_type.ai_socktype = SOCK_DGRAM;
//Get the address info (like IP address) and store in server_info struct
if ((err = getaddrinfo(argv[1], SERVERPORT, &addr_type, &server_info)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(err));
return 1;
}
// There might be multiple IP addresses...loop through and use the first one that works
for(p = server_info; p != NULL; p = p->ai_next) {
if ((sock = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("Error when creating socket");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "Client failed to create socket\n");
return 2;
}
char s[INET_ADDRSTRLEN];
inet_ntop(AF_INET,(struct sockaddr_in *)p->ai_addr,s, sizeof s);
printf("sending to %s....\n",s);
if ((numbytes = sendto(sock, argv[2], strlen(argv[2]), 0,
p->ai_addr, p->ai_addrlen)) == -1) {
perror("Error sending message");
exit(1);
}
printf("client sent %d bytes to %s\n", numbytes, argv[1]);
freeaddrinfo(server_info);
close(sock);
return 0;
}
The lines I am particularly stuck on is:
char s[INET_ADDRSTRLEN];
inet_ntop(AF_INET,(struct sockaddr_in *)p->ai_addr,s, sizeof s);
printf("sending to %s....\n",s);
For example I run the program with ./client www.google.com hello and get the following:
sending to 2.0.19.86....
client sent 5 bytes to www.google.com
I run the program again with ./client localhost hello and inet_ntop still returns the same IP.
sending to 2.0.19.86....
client sent 5 bytes to localhost
No errors are being thrown when I am creating the socket, and the message sends successfully when I send it to the receiving program over localhost, why is inet_ntop still outputting this weird address?

Answer 1

In your call to inet_ntop:
inet_ntop(AF_INET,(struct sockaddr_in *)p->ai_addr,s, sizeof s);
You're not passing in the correct structure. When AF_INET is passed as the first argument, the second argument should have type struct in_addr *, not struct sockaddr_in *.
You need to call out the sin_addr member which is of this type.
inet_ntop(AF_INET, &((struct sockaddr_in *)p->ai_addr)->sin_addr, s, sizeof s);