Question

Below is my code:

#include <stdio.h>
#include <string.h>
#include <curl/curl.h>

/* Auxiliary function that waits on the socket. */ 
static int wait_on_socket(curl_socket_t sockfd, int for_recv, long timeout_ms)
{
  struct timeval tv;
  fd_set infd, outfd, errfd;
  int res;

  tv.tv_sec = timeout_ms / 1000;
  tv.tv_usec= (timeout_ms % 1000) * 1000;

  FD_ZERO(&infd);
  FD_ZERO(&outfd);
  FD_ZERO(&errfd);

  FD_SET(sockfd, &errfd); /* always check for error */ 

  if(for_recv)
  {
    FD_SET(sockfd, &infd);
  }
  else
  {
    FD_SET(sockfd, &outfd);
  }

  /* select() returns the number of signalled sockets or -1 */ 
  res = select(sockfd + 1, &infd, &outfd, &errfd, &tv);
  return res;
}

int main(void)
{
  CURL *curl;
  CURLcode res;
  /* Minimalistic http request */ 
  const char *request = "reactantsJSON={\"O=O\":{\"N\":1}}&productsJSON=[\"O=O\",\"[O]\"]&temperature=2273.15&pressure=101.325";
  curl_socket_t sockfd; /* socket */ 
  long sockextr;
  size_t iolen;

  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://gibbs.sdsu.edu:8080/axis2/services/GibbsMinimization/solveTP");
    /* Do not do the transfer - only connect to host */ 
    curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
    res = curl_easy_perform(curl);

    if(CURLE_OK != res)
    {
      printf("Error: %s\n", strerror(res));
      return 1;
    }

    /* Extract the socket from the curl handle - we'll need it for waiting.
     * Note that this API takes a pointer to a 'long' while we use
     * curl_socket_t for sockets otherwise.
     */ 
    res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockextr);

    if(CURLE_OK != res)
    {
      printf("Error: %s\n", curl_easy_strerror(res));
      return 1;
    }

    sockfd = sockextr;

    /* wait for the socket to become ready for sending */ 
    if(!wait_on_socket(sockfd, 0, 60000L))
    {
      printf("Error: timeout.\n");
      return 1;
    }

    puts("Sending request.");
    /* Send the request. Real applications should check the iolen
     * to see if all the request has been sent */ 
    res = curl_easy_send(curl, request, strlen(request), &iolen);

    if(CURLE_OK != res)
    {
      printf("Error: %s\n", curl_easy_strerror(res));
      return 1;
    }
    puts("Reading response.");

    /* read the response */ 
    for(;;)
    {
      char buf[1024];

      wait_on_socket(sockfd, 1, 60000L);
      res = curl_easy_recv(curl, buf, 1024, &iolen);

      if(CURLE_OK != res)
        break;

      printf("Received %u bytes.\n", iolen);

    }

    /* always cleanup */ 
    curl_easy_cleanup(curl);
  }
  return 0;
}

I am sending a Json string and the response I am expecting is an XML document. When I compile my code it compiles without errors. But for some reason it is not going in the for loop for the receive function. Any kind of help would be appreciated. thanks in advance.

Answer 1

$ gdb ./a.out
GNU gdb (GDB) 7.2-ubuntu
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from a.out...done.
(gdb) b 98
Breakpoint 1 at 0x400f5d: file c.c, line 98.
(gdb) run
Starting program: a.out
[Thread debugging using libthread_db enabled]
Sending request.
Reading response.

Breakpoint 1, main () at c.c:99
99            if(CURLE_OK != res)
(gdb) p res
$1 = CURLE_UNSUPPORTED_PROTOCOL
(gdb)

you have to put everything after the 1st slash in request instead of in curl_easy_setopt, so

curl_easy_setopt(curl, CURLOPT_URL, "http://gibbs.sdsu.edu:8080");

and

const char *request = "GET /axis2/services/GibbsMinimization/solveTP?reactantsJSON={\"O=O\":{\"N\":1}}&productsJSON=[\"O=O\",\"[O]\"]&temperature=2273.15&pressure=101.325 HTTP/1.0\r\n\r\n";

cause of you’re doing the http request manually

also, way to initialize buf with all zeroes is

char buf[1024]={0};