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  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">
<task id="GUID-AB7E58EB-F698-4CAD-B9BF-ECE712C6DB04" xml:lang="en"><title>Create
the service class</title><prolog><metadata><keywords/></metadata></prolog><taskbody>
<context>       <p>Create the server service support class, derived from <codeph>CApaAppServiceBase</codeph> or
a suitable System-GUI specialization of this class. This class adapts the
IPC protocol to a set of virtual functions which the server application can
override to implement the service. This class has the following responsibilities:</p><ul>
<li><p>Receiving and decoding the IPC messages from the client</p></li>
<li><p>Defining and calling virtual functions which the server application
can override to implement the service</p></li>
<li><p>Checking all parameters sent from the client for validity </p></li>
<li><p>Supporting the security policy of the server application for this service.</p></li>
</ul><p>This example shows a server-side service support class for a chat
service. This class implements the code necessary for sending messages to
the client, but provides a pure virtual <codeph>Receive()</codeph> function
for the server application to implement its own handling of messages received
from the client.</p><codeblock xml:space="preserve">class CChatService : public CApaAppServiceBase
    {
    public:
        CChatService();
        ~CChatService();
        void Send(const TDesC&amp; aMessage);
        virtual void Receive(TDes&amp; aMessage) = 0;
    private:
        void ServiceL(const RMessage2&amp; aMessage);
        TBool ReceivePending() const;
    private:
        RMessagePtr2 iReceiveMsg;
        TInt iReceiveLen;
    };
</codeblock></context>
</taskbody></task>