Having trouble compiling tutorial program :S

[Matty_Alan]

Hi, im trying to compile some code right out of beej's tutorial but at compile time it comes up with a whole array of errors i'ved linked libwsock32.a, included winsock.h and ran the WSAstartup code (also cut and pasted directly out of the book) like the tutoiral says too but it's got me stumped.

Here are the errors im getting:

getaddrinfo undecleared first use of function
gai_strerror undecleared first use of function
inet_ntop undecleared first use of function
freeaddrinfo undecleared first use of function
invalid use of undefined type `struct sockaddr_in6'
forward declaration of `struct sockaddr_in6'

and heres the code:

/*
** showip.c -- show IP addresses for a host given on the command line
*/


#include <stdio.h>
#include <string.h>
#include <sys/types.h>
//#include <sys/socket.h>
//#include <netdb.h>
//#include <arpa/inet.h>
#include <winsock.h>

struct addrinfo {
int ai_flags; // AI_PASSIVE, AI_CANONNAME, etc.
int ai_family; // AF_INET, AF_INET6, AF_UNSPEC
int ai_socktype; // SOCK_STREAM, SOCK_DGRAM
int ai_protocol; // use 0 for "any"
size_t ai_addrlen; // size of ai_addr in bytes
struct sockaddr *ai_addr; // struct sockaddr_in or _in6
char *ai_canonname; // full canonical hostname
struct addrinfo *ai_next; // linked list, next node
};


int main(int argc, char *argv[])
{
    WSADATA wsaData; // if this doesn't work
//  WSAData wsaData; // then try this instead
// MAKEWORD(1,1) for Winsock 1.1, MAKEWORD(2,0) for Winsock 2.0:
if (WSAStartup(MAKEWORD(1,1), &wsaData) != 0) {
fprintf(stderr, "WSAStartup failed.\n");
exit(1);
}
    
    
struct addrinfo hints, *res, *p;
int status;
char ipstr[INET6_ADDRSTRLEN];
if (argc != 2) {
fprintf(stderr,"usage: showip hostname\n");
return 1;
}
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
hints.ai_socktype = SOCK_STREAM;
if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
return 2;
}
printf("IP addresses for %s:\n\n", argv[1]);
for(p = res;p != NULL; p = p->ai_next) {
void *addr;
char *ipver;
// get the pointer to the address itself,
// different fields in IPv4 and IPv6:
if (p->ai_family == AF_INET) { // IPv4
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
addr = &(ipv4->sin_addr);
ipver = "IPv4";
} else { // IPv6
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
addr = &(ipv6->sin6_addr);
ipver = "IPv6";
}
// convert the IP to a string and print it:
inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
printf(" %s: %s\n", ipver, ipstr);
}
freeaddrinfo(res); // free the linked list
return 0;
}

[DeadPlanet]

It's much easier to read if you post code with proper indentation.

You should link to libws2_32.a instead of libwsock32.a.

You should #include <winsock2.h> instead of winsock.h.

Also, you should comment out #include <sys/types.h>.

Beej's Guide to Network Programming was updated sometime last year and includes more IPv6 friendly functions which (I think) are only included in Winsock 2 on Windows. You might also want to initialise Winsock to 2.0 instead of 1.1 when you call WSAStartup, and also call WSACleanup once you are done.

Also remember that on windows, close is closesocket (which I don't think you have used anyway, but it's good to know).

[Matty_Alan]

It's much easier to read if you post code with proper indentation.

Yea sorry about that I was in a bit of a rush so i didn't clean up the code.

[Matty_Alan]

Ok iv'e tried linking the new winsock and changing the headers but it's still comming up with the same error(s),

Errors:

'getaddrinfo' undeclared (first use this function) 
'freeaddrinfo' undeclared (first use this function)

here's a simpler version of the code that comes up with the same errors

#include <winsock2.h>

struct addrinfo {
int ai_flags;              // AI_PASSIVE, AI_CANONNAME, etc.
int ai_family;             // AF_INET, AF_INET6, AF_UNSPEC
int ai_socktype;           // SOCK_STREAM, SOCK_DGRAM
int ai_protocol;           // use 0 for "any"
size_t ai_addrlen;         // size of ai_addr in bytes
struct sockaddr *ai_addr;  // struct sockaddr_in or _in6
char *ai_canonname;        // full canonical hostname
struct addrinfo *ai_next;  // linked list, next node
};

int main()
{
    char a = 'b';
    int status;

    struct addrinfo hints, *res, *p;

    WSADATA wsaData;
    
    WSAStartup(MAKEWORD(2,0), &wsaData);

    status = getaddrinfo(a, NULL, &hints, &res);
    
    freeaddrinfo(res);
    
    return 0;
    
   }

[Matty_Alan]

oh... and This is how iv'e linked it:

[vart]

getaddrinfo Function (Windows)

Scroll to the end of the page

Find Requirements

And look at the required header file to be included

[DeadPlanet]

If the way you linked doesn't work (I'm using Code::Blocks, I'd say it's the same but it may work) then use -lws2_32 as the linker argument instead.

vart said it, Microsoft has fairly good documentation, please try to consult it first.

[Matty_Alan]

Oh that worked fine i just needed to add the ws2tcpip header thanx for that