Symbian OS中的Client/Server机制分析

核心提示：IMPORT_C virtual ~CSession2() =0;public:inline const CServer2* Server() const;IMPORT_C void ResourceCountMarkStart();IMPORT_C void ResourceCountMarkEnd(const RM

IMPORT_C virtual ~CSession2() =0;

public:

inline const CServer2* Server() const;

IMPORT_C void ResourceCountMarkStart();

IMPORT_C void ResourceCountMarkEnd(const RMessage2& aMessage);

IMPORT_C virtual TInt CountResources();

/**

Handles the servicing of a client request that has been passed to the server.

This function must be implemented in a derived class. The details of the request are contained within the message.

@param aMessage The message containing the details of the client request.

*/

virtual void ServiceL(const RMessage2& aMessage) =0;

IMPORT_C virtual void ServiceError(const RMessage2& aMessage,TInt aError);

...

...

};

virtual void ServiceL(const RMessage2& aMessage) =0;

这个是纯虚函数，所以派生类必须做实现。当Client在建立了和Server的连接后，会通过某个接口向Server发送数据请求等操作，Server端的Session的虚函数ServiceL()会被调用，在参数RMessage2中会包括Client的请求信息。根据 aMessage.Function()的值做相应的处理。处理完后调用aMessage.Complete( KErrNone );来告知Client处理结束了，通常是增加请求线程上的信号量来告诉Client请求的完成。

既然，Server端有个Session，那么Client端也有个相应的Session了，答案是肯定的。它就是RSessionBase ，它是Client端的Session句柄，通过这个Client端的接口就可以和Server通信了。

/**

Clients normally define and implement a derived class to provide a richer interface.

*/

class RSessionBase : public RHandleBase

{

friend class RSubSessionBase;

。。。

IMPORT_C TInt Open(RMessagePtr2 aMessage,TInt aParam,TOwnerType aType=EOwnerProcess);

IMPORT_C TInt Open(RMessagePtr2 aMessage,TInt aParam,const TSecurityPolicy& aServerPolicy,TOwnerType aType=EOwnerProcess);

IMPORT_C TInt Open(TInt aArgumentIndex, TOwnerType