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Creating a Service

Creating a Web service is greatly simplified in WWSAPI by the Service Model API and the WsUtil.exe tool. The Service Model provides an API that enables the service and client to send and receive messages over a channel as C method calls. The WsUtil tool generates stubs and headers for implementing the service.

Implementing a Calculator Service using WWSAPI

Using the generated sources from the Wsutil.exe tool, implement the service by the following steps.

Include the headers in your application source.

#include "CalculatorProxyStub.h"

Implement the service operations. In this example, the service operations are the Add and Subtract functions of the calculator service.

HRESULT CALLBACK Add (const WS_OPERATION_CONTEXT* context, 
                  int a, int b, int* result, 
                  const WS_ASYNC_CONTEXT* asyncContext, 
                  WS_ERROR* error)
{
    *result = a + b;
    printf ("%d + %d = %d\n", a, b, *result);
    return NOERROR;
}

HRESULT CALLBACK Subtract (const WS_OPERATION_CONTEXT* context, 
                  int a, int b, int* result, 
                  const WS_ASYNC_CONTEXT* asyncContext, 
                  WS_ERROR* error)
{
    *result = a - b;
    printf ("%d - %d = %d\n", a, b, *result);
    return NOERROR;
}

Define the service contract by setting the fields of a WS_SERVICE_CONTRACT structure.

static const DefaultBinding_ICalculatorFunctionTable calculatorFunctions = {Add, Subtract};
static const WS_SERVICE_CONTRACT calculatorContract = 
{
    &DefaultBinding_ICalculatorContractDesc, // comes from the generated header.
    NULL, // for not specifying the default contract
    &calculatorFunctions // specified by the user
};

Now, create a service host and open it for communication.

WS_SERVICE_ENDPOINT serviceEndpoint = {0};
serviceEndpoint.uri.chars = L"http://+:80/example"; // address given as uri
serviceEndpoint.binding.channelBinding =  WS_HTTP_CHANNEL_BINDING; // channel binding for the endpoint
serviceEndpoint.channelType = WS_CHANNEL_TYPE_REPLY; // the channel type
serviceEndpoint.uri.length = (ULONG)wcslen(serviceEndpoint.uri.chars);
serviceEndpoint.contract = (WS_SERVICE_CONTRACT*)&calculatorContract;  // the contract
serviceEndpoint.properties = serviceProperties;
serviceEndpoint.propertyCount = WsCountOf(serviceProperties);

if (FAILED (hr = WsCreateServiceHost (&serviceEndpoint, 1, NULL, 0, &host, error)))
    goto Error;

// WsOpenServiceHost  to start the listeners in the service host 
if (FAILED (hr = WsOpenServiceHost (host, NULL, error)))
    goto Error;

Please refer to the code example at HttpCalculatorServiceExample for a full implementation of the calculator service.

 

 

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