Sending SOAP request using libcurl - c

Question

I could understand the examples of simple sendrecv for sending REST request using libcurl. Now i want to send a SOAP request using libcurl. I have changed the REST request code to achieve the same, but the code is not working. My code is:
#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 = "<?xml version="1.0" encoding="utf-8"?>
<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:tns="http://ThermodynamicProperties/">
<S:Body>
<tns:getSpeciesInformation>
<speciesSymbol>CO2</speciesSymbol>
<phase>GAS</phase>
</tns:getSpeciesInformation>
</S:Body>
</S:Envelope>";
curl_socket_t sockfd; /* socket */
long sockextr;
size_t iolen;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://thermo.sdsu.edu/servlet/ThermodynamicProperties/ThermodynamicPropertiesService");
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 1);
curl_easy_setopt(curl, CURLOPT_POST, 1);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, request);
/* 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;
}
I feel that I am not doing correct in building the SOAP request. Any help would be great as this is a completely new field for me.

Answer 1

SOAP messages are much more complex than REST messages.
My advice would be to download one of the better SOAP utilities like "SOAPUI" and use this to build and test a well formed SOAP request. Once you have a working request you can paste this into your C program.
Also I would recommend using a library like libxml2 (or Xerces if you dont mind C++) to build your SOAP messages if you are doing anything more complex than sending a simple pre formatted request.
SOAPUI is a java based test utility SOAP services. It can generate messages form a given WSDL, generate responses, browse messages etc.
More info here: SOAPUI