C/UNIX: port scanner - c

Question

I need program that find all web servers into file that contains IP addresses.
I found that IP address is server if his port 80 is open. And I wrote this code but it doesn't work. Аlways sayd that port 80 is closed, even i write IP with open port 80. (194.153.145.104 for example). Where I wrong?
I'm cheking here for IP's with open ports: http://www.yougetsignal.com/tools/open-ports/
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdio.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
u_short port=80; /* user specified port number */
short int sock = -1; /* the socket descriptor */
struct hostent *host_info; /* host info structure */
struct sockaddr_in address; /* address structures */
char addr[1023];
char buf[20];
char *filename;
filename=argv[1];
FILE *file = fopen( filename, "r" );
while (!feof(file))
{
fscanf(file,"%s",buf);
strncpy(addr, buf, 1023);
bzero((char *)&address, sizeof(address));
address.sin_addr.s_addr = inet_addr(addr);
address.sin_port = htons(port);
address.sin_family=AF_INET;
sock = socket(PF_INET, SOCK_STREAM, 0);
if (sock == -1) {
fprintf(stderr, "Error: could not assign master socket\n");
exit (1);
}
if(connect(sock,(struct sockaddr *)&address,sizeof(address)) == 0)
printf("%s is a web server\n", addr);
else printf("%s isn't a web server\n", addr);
close(sock);
}
return 0;
}

Answer 1

Did you compile with warnings enabled? Using gcc I added -Wall, which says inet_addrisnt declared right. Including <arpa/inet.h> makes the program work just fine.
I suggest checking the return values of all functions and system calls you use, as to detect and locate any possible errors.
Sample output:
$ ./a.out ip.txt
127.0.0.1 is a web server
127.0.0.1 isn't a web server
EDIT: Adding some more details about my test setup, since it still does not work for the OP.
Added the include for <arpa/inet.h>
Compiled with gcc -Wall -O0 http_port_scan.c
Set up a listener on port 80 with: sudo nc -l 80
Executed: ./a.out ip.txt
The file ip.txt looks like:
~/src/so$ cat ip.txt
127.0.0.1
thuovila#glx:~/src/so$ file ip.txt
ip.txt: ASCII text
On this computer I get two lines saying "is a web server" since the nc is closed slower than my other computer. The execution environment is Ubuntu LTS 12.04 with the uname -a: Linux glx 3.2.0-43-generic #68-Ubuntu SMP Wed May 15 03:33:33 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
My suggestion is still, that you add checking for all the return values of functions and if they fail, call perror() or use some other means to figure out the error.