NdrSendReceive access denied in RPC program

i followed this tutorial about creating a server and client program using RPC and downloaded the source code from it http://www.aspfree.com/c/a/net/introduction-to-rpc-on-windows-part-i/

but when i ran the code "Runtime exception occured: 5" displayed which i know means access denied.

i debugged the program and found that the problem was with the line

NdrSendReceive( (PMIDL_STUB_MESSAGE) &_StubMsg, (unsigned char __RPC_FAR *) _StubMsg.Buffer );

here is the full show function:

  void Show( 
    /* [string][in] */ const unsigned char __RPC_FAR *szMsg)
{

    RPC_BINDING_HANDLE _Handle  =   0;

    RPC_MESSAGE _RpcMessage;

    MIDL_STUB_MESSAGE _StubMsg;

    if(!szMsg)
        {
        RpcRaiseException(RPC_X_NULL_REF_POINTER);
        }
    RpcTryFinally
        {
        NdrClientInitializeNew(
                          ( PRPC_MESSAGE  )&_RpcMessage,
                          ( PMIDL_STUB_MESSAGE  )&_StubMsg,
                          ( PMIDL_STUB_DESC  )&DoRPC_StubDesc,
                          0);


        _Handle = hDoRPCBinding;


        _StubMsg.BufferLength = 12U;
        NdrConformantStringBufferSize( (PMIDL_STUB_MESSAGE) &_StubMsg,
                                       (unsigned char __RPC_FAR *)szMsg,
                                       (PFORMAT_STRING) &__MIDL_TypeFormatString.Format[4] );

        NdrGetBuffer( (PMIDL_STUB_MESSAGE) &_StubMsg, _StubMsg.BufferLength, _Handle );

        NdrConformantStringMarshall( (PMIDL_STUB_MESSAGE)& _StubMsg,
                                     (unsigned char __RPC_FAR *)szMsg,
                                     (PFORMAT_STRING) &__MIDL_TypeFormatString.Format[4] );

        NdrSendReceive( (PMIDL_STUB_MESSAGE) &_StubMsg, (unsigned char __RPC_FAR *) _StubMsg.Buffer );

        }
    RpcFinally
        {
        NdrFreeBuffer( (PMIDL_STUB_MESSAGE) &_StubMsg );

        }
    RpcEndFinally

}

and here's some code from main:

RpcTryExcept
    {
        // Calls the RPC function. The hDoRPCBinding binding handle
        // is used implicitly.
        // Connection is done here.
        const unsigned char szMsg[] = "Client: I Can RPC Now!";
        Show(szMsg);
    }
    RpcExcept(1)
    {
        printf("Runtime exception occured: %d\n",RpcExceptionCode());
    }
    RpcEndExcept

so when debugging it jumped to the RpcExcept line when it reached NdrSendReceive
please help i have no idea how to fix this problem

Tags: C++, Visual Studio, TCP/IP, Remote