working with a URL in C++

dpalyca755
dpalyca755 used Ask the Experts™
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How do I read and write to a URL using C++?
Are there libs built in like there are in java?
I am seeking some examples and good reference material.
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C++ uses sockets, here is some good reference material:

http://www.alhem.net/Sockets/tutorial/
jkr
Top Expert 2012
Commented:
>>Are there libs built in like there are in java?

Not build in ones, but free 3rd party libs like cURL (http://curl.haxx.se/libcurl/). See the samples at http://curl.haxx.se/libcurl/c/simple.html for reading from an URL:

#include <stdio.h>
#include <curl/curl.h>
 
int main(void)
{
  CURL *curl;
  CURLcode res;
 
  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
    res = curl_easy_perform(curl);
 
    /* always cleanup */ 
    curl_easy_cleanup(curl);
  }
  return 0;
}

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And a PUT request would look like http://curl.haxx.se/libcurl/c/httpput.html

#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
 
#include <curl/curl.h>
 
/*
 * This example shows a HTTP PUT operation. PUTs a file given as a command
 * line argument to the URL also given on the command line.
 *
 * This example also uses its own read callback.
 *
 * Here's an article on how to setup a PUT handler for Apache:
 * http://www.apacheweek.com/features/put
 */ 
 
static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *stream)
{
  size_t retcode;
  curl_off_t nread;
 
  /* in real-world cases, this would probably get this data differently
     as this fread() stuff is exactly what the library already would do
     by default internally */ 
  retcode = fread(ptr, size, nmemb, stream);
 
  nread = (curl_off_t)retcode;
 
  fprintf(stderr, "*** We read %" CURL_FORMAT_CURL_OFF_T
          " bytes from file\n", nread);
 
  return retcode;
}
 
int main(int argc, char **argv)
{
  CURL *curl;
  CURLcode res;
  FILE * hd_src ;
  int hd ;
  struct stat file_info;
 
  char *file;
  char *url;
 
  if(argc < 3)
    return 1;
 
  file= argv[1];
  url = argv[2];
 
  /* get the file size of the local file */ 
  hd = open(file, O_RDONLY) ;
  fstat(hd, &file_info);
  close(hd) ;
 
  /* get a FILE * of the same file, could also be made with
     fdopen() from the previous descriptor, but hey this is just
     an example! */ 
  hd_src = fopen(file, "rb");
 
  /* In windows, this will init the winsock stuff */ 
  curl_global_init(CURL_GLOBAL_ALL);
 
  /* get a curl handle */ 
  curl = curl_easy_init();
  if(curl) {
    /* we want to use our own read function */ 
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);
 
    /* enable uploading */ 
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
 
    /* HTTP PUT please */ 
    curl_easy_setopt(curl, CURLOPT_PUT, 1L);
 
    /* specify target URL, and note that this URL should include a file
       name, not only a directory */ 
    curl_easy_setopt(curl, CURLOPT_URL, url);
 
    /* now specify which file to upload */ 
    curl_easy_setopt(curl, CURLOPT_READDATA, hd_src);
 
    /* provide the size of the upload, we specicially typecast the value
       to curl_off_t since we must be sure to use the correct data size */ 
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
                     (curl_off_t)file_info.st_size);
 
    /* Now run off and do what you've been told! */ 
    res = curl_easy_perform(curl);
 
    /* always cleanup */ 
    curl_easy_cleanup(curl);
  }
  fclose(hd_src); /* close the local file */ 
 
  curl_global_cleanup();
  return 0;
}

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Doing that on a socket level would be overkill.
InternetReadFile() is available on Windows - not as much control as the general WinInet API but is quick and dirty to get data from a connection.

http://msdn.microsoft.com/en-us/library/windows/desktop/aa385103(v=vs.85).aspx
http://support.microsoft.com/kb/149413


The cURL libraries recommended by jkr offer portability across platforms

Cheers,
   Chris

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