Building a C++ client using gSOAP

When you create a web service in gSOAP, it is easy to create a client in parallel. gSOAP is a very good package, which appears more complicated to use initially than it actually is. Most of the hard work in done for you with a couple of scripts, and pretty much all you have to do is fill in the actual functionality you require in the service and the client.

C++ probably wouldn't be my first choice to write a client in, but it isn't too much harder than the Python client - particularly given the excellent documentation available. Once you have gSOAP installed, the process is as follows.

Accessing the service using WSDL

Firstly you must obtain the publicly available WSDL file and run the WSDL parser, which creates a C++ (or C) header file:

phoenix% wsdl2h -o quanta.h quanta.wsdl 

You then run the gSOAP Stub and Skeleton compiler on the header file (you may have to copy some of the standard header files - like stl.h - from the gSOAP installation into your current directory):

phoenix% soapcpp2 quanta.h

The header file allows you to work out what methods are available and how they should be called. Firstly there is the general information about the service:

// Service quanta : gSOAP 2.6.0 generated service definition
//gsoap ns1 service name:       quanta 
//gsoap ns1 service type:       quanta 
//gsoap ns1 service port:       http://phoenix:18080/ 
//gsoap ns1 service namespace:  urn:atnf-aips-quanta 

/* Service quanta operations:
  ns1__has_USCOREunit
  ns1__has_USCOREconstant
  ns1__has_USCOREprefix
  ns1__list_USCOREunits
  ns1__list_USCOREprefixes
  ns1__can_USCOREconvert
  ns1__converts
  ns1__convertf
  ns1__convert_USCOREtobase
  ns1__convert_USCOREtable
*/

// Operation convert_USCOREtobase : 
// Service definition of function ns1__convert_USCOREtobase
int ns1__convert_USCOREtobase(std::string* quantity,
  struct ns1__convert_USCOREtobaseResponse {
    std::string* result;
  } & );

From this information we can write a client program to access the convert_tobase function:

#include 
#include 

#include "soapH.h"
#include "quanta.nsmap"
                                                                                
using namespace std;

int main(int argc, char **argv){
  struct soap soap;
  string result
  string input = argv[1]
  string endpoint = "http://phoenix:18080/quanta"
  struct ns1__convert_USCOREtobaseResponse response;

  soap_init(&soap);
  if(soap_call_ns1__convert_USCOREtobase(&soap, endpoint, "", &input, response))
    soap_print_fault(&soap, stderr);
  cout << *response.result << endl;

  soap_end(&soap);
  soap_done(&soap);
  return 0;
}

phoenix% g++ soapC.cpp soapClient.cpp stdsoap2.cpp client.cc -o client
phoenix% ./client '10km/s'
10000 m/s

In this explanation I have skipped over some details - mainly to do with installation and compiling. These are discussed further on the WIKI page.