Cannot Connect to HTTP Service Via Socket - C

Question

I'm writing a client program that establishes a socket, connects to a remote server, and issues an HTTP request. However, I can't seem to connect to the remote server.

I believe I've done everything right, and even set up the correct port # for the sockaddr_in, but still I can't connect.

What am I missing?

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

int main(int argc, char *argv[])
{
    FILE *fout;

    int i, c, sk;
    char *tk, host[64], path[64], fname[64], http_msg[256], buf[1024];

    struct sockaddr_in remote;
    struct hostent *hp;
    struct servent *se;

    if(argc != 2)
    {
        printf("Invalid number of arguments. Program terminating...\n");
        exit(1);
    }

    sk = socket(AF_INET, SOCK_STREAM, 0);
    remote.sin_family = AF_INET;

    c = 0;
    tk = strtok(argv[1], "/");
    while(tk != NULL)
    {
        if(c == 0)
            strcpy(host, tk);
        else if(c == 1)
            strcpy(path, tk);
        else
            strcpy(fname, tk);
        ++c;
        tk = strtok(NULL, "/");
    }

    snprintf(http_msg, 256, "GET /%s/%s HTTP/1.1\r\nHost: %s\r\nConnection: close\r\n\n", path, fname, host);

    hp = gethostbyname(host);
    if(hp == NULL)
    {
        printf("Can't find host %s. Program terminating...\n", host);
        exit(1);
    }

    se = getservbyname("http", "tcp");
    remote.sin_port = ntohs(se->s_port);

    if(connect(sk, (struct sockaddr*)&remote, sizeof(remote)) < 0)
    {
        printf("Connection attempt failed. Program terminating...\n");
        exit(1);
    }

    send(sk, http_msg, sizeof(http_msg) + 1, 0);
    recv(sk, buf, sizeof(buf), 0);
    printf("%s\n", buf);

    return 0;
}

You missed to inject hp into remote: bcopy((char *)hp->h_addr, (char *)&remote.sin_addr.s_addr, hp->h_length); — Ôrel
– Ôrel, Commented Apr 7, 2015 at 4:20
I just tried that and am still not able to connect. Does it matter if I use memcpy instead? — Delfino
– Delfino, Commented Apr 7, 2015 at 4:22
with this line just before the connect, the connection is done. How do you check if you are connected ? — Ôrel
– Ôrel, Commented Apr 7, 2015 at 4:36
Which line? I test the connection with if(connect(sk, (struct sockaddr *)&remote, sizeof(remote)) < 0) — Delfino
– Delfino, Commented Apr 7, 2015 at 4:40

Ôrel · Accepted Answer · 2015-04-07 05:06:42Z

I got it

the problem is with the line

remote.sin_port = ntohs(se->s_port);

You don't need to convert it. This code works for me:

if(argc != 2)                                                              
{                                                                          
    printf("Invalid number of arguments. Program terminating...\n");       
    exit(1);                                                               
}                                                                          

bzero(&remote, sizeof(remote));                                            
sk = socket(AF_INET, SOCK_STREAM, 0);                                      
remote.sin_family = AF_INET;                                               

c = 0;                                                                     
tk = strtok(argv[1], "/");                                                 
while(tk != NULL)                                                          
{                                                                          
    if(c == 0)                                                             
        strcpy(host, tk);                                                  
    else if(c == 1)                                                        
        strcpy(path, tk);                                                  
    else                                                                   
        strcpy(fname, tk);                                                 
    ++c;                                                                   
    tk = strtok(NULL, "/");                                                
}                                                                          

snprintf(http_msg, 256, "GET /%s/%s HTTP/1.1\r\nHost: %s\r\nConnection: close\r\n\r\n", path, fname, host); 

hp = gethostbyname(host);                                                  
if(hp == NULL)                                                             
{                                                                          
    printf("Can't find host %s. Program terminating...\n", host);          
    exit(1);                                                               
}                                                                          

se = getservbyname("http", "tcp");                                         
printf("%d port\n", ntohs(se->s_port));                                    
remote.sin_port = se->s_port;                                              
bcopy((char *)hp->h_addr, (char *)&remote.sin_addr.s_addr, hp->h_length);  

if(connect(sk, (struct sockaddr*)&remote, sizeof(remote)) < 0)             
{                                                                          
    printf("Connection attempt failed. Program terminating...\n");         
    exit(1);                                                               
}                                                                          

send(sk, http_msg, sizeof(http_msg) + 1, 0);                               
recv(sk, buf, sizeof(buf), 0);                                             
printf("%s\n", buf);                                                       

return 0;

}

Why use bzero for remote? And I will try that. Unfortunately I'm not at my computer right now.
Stack value are not initialized, so you have to init it. By default I prefer to reset to 0, to be sure

Liviu valentyn · Accepted Answer · 2015-04-07 04:47:59Z

0

Do this:

remote.sin_port = ntohs(se->s_port);
remote.sin_family = AF_INET;
remote.sin_addr = *((struct in_addr *) hp->h_addr);

That shoul'd do it. See the \r\n\r\n after Connection: close.

snprintf(http_msg, 256, "GET /%s/%s HTTP/1.1\r\nHost: %s\r\nConnection: close\r\n\r\n", path, fname, host);

edited Apr 7, 2015 at 4:47

answered Apr 7, 2015 at 4:16

Liviu valentyn

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