How to send soap(xml) request using libcurl - c++

Question

I am trying to send a SOAP request in xml format to a SOAP service using libcurl but i am getting error like" 500 internal server error" while posting the request in soap service.
I have tried almost all the approaches available online.
#include <stdio.h>
#include <curl/curl.h>
int main()
{
FILE * wfp = fopen("res.xml", "w+"); //File pointer to write the soap response
if (!wfp) {
perror("Write File Open:");
// exit(0);
}
struct curl_slist *header = NULL;
header = curl_slist_append(header, "Content-type: text/xml; charset=utf-8");
header = curl_slist_append(header, "SOAPAction: http://localhost:62634/Service1.svc");
header = curl_slist_append(header, "Transfer-Encoding: chunked");
header = curl_slist_append(header, "Expect:");
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://localhost:62634/Service1.svc");
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "<?xml version=\"1.0\" encoding=\"UTF-8\"?><soapenv:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:AddNumbers=\"http://localhost:62634/Service1.svc\"><soapenv:Header/><soapenv:Body><AddNumbers xmlns=\"http://tempuri.org/\"><number1>4</number1><number2>5</number2></AddNumbers></soapenv:Body></soapenv:Envelope>");
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data); //Gets data to be written to file
curl_easy_setopt(curl, CURLOPT_WRITEDATA, wfp); //Writes result to file
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, header);
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE_LARGE, (curl_off_t)-1);
//curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
return 1;
}
}