I have very simple C program that gets the ip addresses for a host name as
follows:
#include<stdio.h> //printf
#include<string.h> //memset
#include<stdlib.h> //for exit(0);
#include<sys/socket.h>
#include<errno.h> //For errno - the error number
#include<netdb.h> //hostent
#include<arpa/inet.h>
int hostname_to_ip(char * , char *);
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <netinet/in.h>
int main(int argc , char *argv[])
{
printf("In main\n");
char *hostname = "www.google.com";
char ip[100];
hostname_to_ip(hostname , ip);
printf("%s x resolved to %s" , hostname , ip);
}
/*
Get ip from domain name
*/
int hostname_to_ip(char * hostname , char* ip)
{
printf("hostname %s\n", hostname);
struct hostent *he;
struct in_addr **addr_list;
int i;
he = gethostbyname( hostname );
printf("name %s\n", he->h_name);
printf("addrtype %d\n", he->h_addrtype);
if ( (he = gethostbyname( hostname) ) == NULL)
{
printf("error");
herror("gethostbyname");
return 1;
}
addr_list = (struct in_addr **) he->h_addr_list;
for(i = 0; addr_list[i] != NULL; i++)
{
printf("address %s\n", inet_ntoa(*addr_list[i]));
}
return 1;
}
On Ubuntu when I compile it with gcc as: gcc socket.c
-L/usr/lib/x86_64-linux-gnu -o socket -lpthread and run it produces
correct ip address. Output:
./socket
In main
hostname www.google.com
name www.google.com
addrtype 2
address 63.117.14.88
address 63.117.14.86
address 63.117.14.84
address 63.117.14.90
address 63.117.14.87
address 63.117.14.89
address 63.117.14.91
address 63.117.14.85
When I compile the same program using the emsdk and emcc as:
emcc socket.c -g4 -v -s "BINARYEN_METHOD='interpret-binary'"
-L/usr/lib/x86_64-linux-gnu -o socket.html and run it with nodejs socket.js
or in a browser with emrun and socket.html it produces the output:
In main
hostname www.google.com
name www.google.com
addrtype 2
address 172.29.1.0
Clearly the ip address in bogus. In debugging socket.js I found the
__inet_pton4_raw (shown below) receives the correct host string
(www.google.com) put generates address 172.29.1.0. This function generates
the same ip address not matter what host name is supplied. I have tried the
emsdk /test socket programs as well with the same results. They work when
compiled with gcc but not with emcc. Any help will be much appreciated.
function __inet_pton4_raw(str) {
var b = str.split('.');
for (var i = 0; i < 4; i++) {
var tmp = Number(b[i]);
if (isNaN(tmp)) return null;
b[i] = tmp;
}
return (b[0] | (b[1] << 8) | (b[2] << 16) | (b[3] << 24)) >>> 0;
}
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