Hi, I installed cygwin recently and wanted to do some network programming with it. Since I have never used unix sockets before, I'm reading Beej's Guide To Network Programming. I took this from section 5.1 and tried to compile it. I get a few errors that I can't figure out :-/.
/*
** 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>
int main(int argc, char *argv[])
{
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;
}Here are my errors:
stuff.c: In function `main':
stuff.c:14: error: storage size of 'hints' isn't known
stuff.c:16: error: `INET6_ADDRSTRLEN' undeclared (first use in this function)
stuff.c:16: error: (Each undeclared identifier is reported only once
stuff.c:16: error: for each function it appears in.)
stuff.c:34: error: dereferencing pointer to incomplete type
stuff.c:40: error: dereferencing pointer to incomplete type
stuff.c:41: error: dereferencing pointer to incomplete type
stuff.c:45: error: dereferencing pointer to incomplete type
stuff.c:46: error: dereferencing pointer to incomplete type
stuff.c:51: error: dereferencing pointer to incomplete type
I added this to my code and got rid of the `INET6_ADDRSTRLEN' undeclared error:
#ifndef INET6_ADDRSTRLEN
#define INET6_ADDRSTRLEN 46
#endif