C Socket Error: "Name or service not known" - c

Question

I'm trying to code a program in C that uses sockets to fetch webpages. My code currently prints successfully the HTML code at some webpages, but not all webpages. In the instances where it does not work I get the following error:
Name or service not known
Can someone please offer me a solution? The error occurs when executing getaddrinfo. I can't seem to figure it out after an extensive search for the answer. Thanks everyone!
My code is as follows:
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <err.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <stdarg.h>
/* "BSIZE" is the size of the buffer we use to read from the socket. */
#define BSIZE 0x1000
/* Quickie function to test for failures. It is actually better to use
a macro here, since a function like this results in unnecessary
function calls to things like "strerror". However, not every
version of C has variadic macros. */
static void fail (int test, const char * format, ...)
{
//printf("here in fail");
if (test) {
va_list args;
va_start (args, format);
vfprintf (stderr, format, args);
va_end (args);
exit (EXIT_FAILURE);
}
}
/* Get the web page and print it to standard output. */
static char * get_page (const char * host)
{
/* Output */
char * htmlCode;
const char * page = "momoe/";
/* "s" is the file descriptor of the socket. */
int s;
struct addrinfo hints, *res, *res0;
int error;
memset (&hints, 0, sizeof(hints));
/* Don't specify what type of internet connection. */
hints.ai_family = PF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo (host, "http", & hints, & res0);
//printf("here 2");
fail (error, gai_strerror(error));
//printf("here3");
s = -1;
for (res = res0; res; res = res->ai_next) {
s = socket (res->ai_family, res->ai_socktype, res->ai_protocol);
fail (s < 0, "socket: %s\n", strerror (errno));
if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
fprintf (stderr, "connect: %s\n", strerror (errno));
close(s);
exit (EXIT_FAILURE);
}
break;
}
freeaddrinfo (res0);
if (s == -1) {
printf("Error with socket file ID");
return "Err";
}
/* "msg" is the request message that we will send to the
server. */
char * msg;
/* "format" is the format of the HTTP request we send to the web
server. */
const char * format =
"GET /%s HTTP/1.0\r\nHost: %s\r\nUser-Agent: fetch.c\r\n\r\n";
/* This holds return values from functions. */
int status;
/* I am using non-standard function "asprintf" for convenience. If
you don't have "asprintf", use "snprintf" with a fixed-size
buffer and check its return value against the length of the
buffer after the call. */
status = asprintf (& msg, format, page, host);
/* Check that "asprintf" succeeded. */
fail (status == -1 || ! msg, "asprintf failed.\n");
/* Send the request. */
status = send (s, msg, strlen (msg), 0);
/* Check it succeeded. The FreeBSD manual page doesn't mention
whether "send" sets errno, but
"http://pubs.opengroup.org/onlinepubs/009695399/functions/send.html"
claims it does. */
fail (status == -1, "send failed: %s\n", strerror (errno));
while (1) {
/* The number of bytes received. */
int bytes;
/* Our receiving buffer. */
char buf[BSIZE+10];
/* Get "BSIZE" bytes from "s". */
bytes = recvfrom (s, buf, BSIZE, 0, 0, 0);
/* Stop once there is nothing left to print. */
if (bytes == 0) {
break;
}
fail (bytes == -1, "%s\n", strerror (errno));
/* Nul-terminate the string before printing. */
buf[bytes] = '\0';
/* Add buffer text to output. */
//printf ("%s", buf);
strncat(htmlCode, buf, strlen(buf));
}
free (msg);
return htmlCode;
}
int main () {
/* Get one of the web pages here. */
char * host = "http://xkcd.com/352";
char * webPage;
//printf("\nhere\n");
webPage = get_page (host);
printf("Print HTML:\n\n%s", webPage);
return 0;
}

Answer 1

It looks like you're passing "http://xkcd.com/352" as the host name. You'll need to parse out the host part and only pass it, eg "xkcd.com"

Answer 2

There are mainly 3 issues in your code,
1. /* Output */
char * htmlCode;
You are not allocating memory for htmlCode variable anywhere in the program.
Ex: char htmlCode[1024*60];
2. const char * page = "momoe/";
Page name you given is not in the proper format.
Ex: const char* page = "Homepage.html"
3. char * host = "http://xkcd.com/352";
webPage = get_page (host);
The value in host variable is in wrong format.
Ex: char *host = "google.com"
You change the program and execute it. It'll work.