wxWidgets/interface/ipc.h

/////////////////////////////////////////////////////////////////////////////
// Name:        ipc.h
// Purpose:     documentation for wxConnection class
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxConnection
    @wxheader{ipc.h}

    A wxConnection object represents the connection between a client
    and a server. It is created by making a connection using a
    wxClient object, or by the acceptance of a
    connection by a wxServer object. The
    bulk of a DDE-like (Dynamic Data Exchange) conversation is
    controlled by calling members in a @b wxConnection object or
    by overriding its members. The actual DDE-based implementation
    using wxDDEConnection is available on Windows only, but a
    platform-independent, socket-based version of this API is
    available using wxTCPConnection, which has the same API.

    An application should normally derive a new connection class from
    wxConnection, in order to override the communication event
    handlers to do something interesting.

    @library{wxbase}
    @category{FIXME}

    @seealso
    wxClient, wxServer, @ref overview_ipcoverview "Interprocess communications
    overview"
*/
class wxConnection : public wxObject
{
public:
    //@{
    /**
        Constructs a connection object. If no user-defined connection
        object is to be derived from wxConnection, then the constructor
        should not be called directly, since the default connection
        object will be provided on requesting (or accepting) a
        connection. However, if the user defines his or her own derived
        connection object, the wxServer::OnAcceptConnection
        and/or wxClient::OnMakeConnection
        members should be replaced by functions which construct the new
        connection object.
        If the arguments of the wxConnection constructor are void then
        the wxConnection object manages its own connection buffer,
        allocating memory as needed. A programmer-supplied buffer cannot
        be increased if necessary, and the program will assert if it is
        not large enough. The programmer-supplied buffer is included
        mainly for backwards compatibility.
    */
    wxConnection();
    wxConnection(void* buffer, size_t size);
    //@}

    //@{
    /**
        Called by the server application to advise the client of a change
        in the data associated with the given item. Causes the client
        connection's OnAdvise() member
        to be called. Returns @true if successful.
    */
    bool Advise(const wxString& item, const void* data, size_t size,
                wxIPCFormat format = wxIPC_PRIVATE);
    bool Advise(const wxString& item, const char* data);
    bool Advise(const wxString& item, const wchar_t* data);
    bool Advise(const wxString& item, const wxString data);
    //@}

    /**
        Called by the client or server application to disconnect from the
        other program; it causes the OnDisconnect()
        message to be sent to the corresponding connection object in the
        other program. Returns @true if successful or already disconnected.
        The application that calls @b Disconnect must explicitly delete
        its side of the connection.
    */
    bool Disconnect();

    //@{
    /**
        Called by the client application to execute a command on the
        server. Can also be used to transfer arbitrary data to the server
        (similar to Poke() in
        that respect). Causes the server connection's OnExec()
        member to be called. Returns @true if successful.
    */
    bool Execute(const void* data, size_t size,
                 wxIPCFormat format = wxIPC_PRIVATE);
    bool Execute(const char* data);
    bool Execute(const wchar_t* data);
    bool Execute(const wxString data);
    //@}

    /**
        Message sent to the client application when the server notifies
        it of a change in the data associated with the given item, using
        Advise().
    */
    virtual bool OnAdvise(const wxString& topic,
                          const wxString& item,
                          const void* data,
                          size_t size,
                          wxIPCFormat format);

    /**
        Message sent to the client or server application when the other
        application notifies it to end the connection. The default
        behaviour is to delete the connection object and return @true, so
        applications should generally override @b OnDisconnect
        (finally calling the inherited method as well) so that they know
        the connection object is no longer available.
    */
    virtual bool OnDisconnect();

    /**
        Message sent to the server application when the client notifies
        it to execute the given data, using Execute().
        Note that there is no item associated with this message.
    */
    virtual bool OnExec(const wxString& topic, const wxString& data);

    /**
        Message sent to the server application when the client notifies it to
        accept the given data.
    */
    virtual bool OnPoke(const wxString& topic, const wxString& item,
                        const void* data,
                        size_t size,
                        wxIPCFormat format);

    /**
        Message sent to the server application when the client calls
        Request(). The
        server's OnRequest() method
        should respond by returning a character string, or @NULL to
        indicate no data, and setting *size. The character string must of
        course persist after the call returns.
    */
    virtual const void* OnRequest(const wxString& topic,
                                  const wxString& item,
                                  size_t* size,
                                  wxIPCFormat format);

    /**
        Message sent to the server application by the client, when the client
        wishes to start an 'advise loop' for the given topic and item. The
        server can refuse to participate by returning @false.
    */
    virtual bool OnStartAdvise(const wxString& topic,
                               const wxString& item);

    /**
        Message sent to the server application by the client, when the client
        wishes to stop an 'advise loop' for the given topic and item. The
        server can refuse to stop the advise loop by returning @false, although
        this doesn't have much meaning in practice.
    */
    virtual bool OnStopAdvise(const wxString& topic,
                              const wxString& item);

    //@{
    /**
        Called by the client application to poke data into the server.
        Can be used to transfer arbitrary data to the server. Causes the
        server connection's OnPoke() member to
        be called. If size is -1 the size is computed from the string
        length of data.
        Returns @true if successful.
    */
    bool Poke(const wxString& item, const void* data, size_t size,
              wxIPCFormat format = wxIPC_PRIVATE);
    bool Poke(const wxString& item, const char* data);
    bool Poke(const wxString& item, const wchar_t* data);
    bool Poke(const wxString& item, const wxString data);
    //@}

    /**
        Called by the client application to request data from the server.
        Causes the server connection's OnRequest()
        member to be called. Size may be @NULL or a pointer to a variable
        to receive the size of the requested item.
        Returns a character string (actually a pointer to the
        connection's buffer) if successful, @NULL otherwise. This buffer
        does not need to be deleted.
    */
    const void* Request(const wxString& item, size_t* size,
                        wxIPCFormat format = wxIPC_TEXT);

    /**
        Called by the client application to ask if an advise loop can be
        started with the server. Causes the server connection's
        OnStartAdvise()
        member to be called. Returns @true if the server okays it, @false
        otherwise.
    */
    bool StartAdvise(const wxString& item);

    /**
        Called by the client application to ask if an advise loop can be
        stopped. Causes the server connection's OnStopAdvise()
        member to be called. Returns @true if the server okays it, @false
        otherwise.
    */
    bool StopAdvise(const wxString& item);
};


/**
    @class wxClient
    @wxheader{ipc.h}

    A wxClient object represents the client part of a client-server
    DDE-like (Dynamic Data Exchange) conversation. The actual
    DDE-based implementation using wxDDEClient is available on Windows
    only, but a platform-independent, socket-based version of this
    API is available using wxTCPClient, which has the same API.

    To create a client which can communicate with a suitable server,
    you need to derive a class from wxConnection and another from
    wxClient. The custom wxConnection class will intercept
    communications in a 'conversation' with a server, and the custom
    wxClient is required so that a user-overridden
    wxClient::OnMakeConnection
    member can return a wxConnection of the required class, when a
    connection is made. Look at the IPC sample and the
    @ref overview_ipcoverview "Interprocess communications overview" for
    an example of how to do this.

    @library{wxbase}
    @category{FIXME}

    @seealso
    wxServer, wxConnection, @ref overview_ipcoverview "Interprocess communications
    overview"
*/
class wxClient : public wxObject
{
public:
    /**
        Constructs a client object.
    */
    wxClient();

    /**
        Tries to make a connection with a server by host (machine name
        under UNIX - use 'localhost' for same machine; ignored when using
        native DDE in Windows), service name and topic string. If the
        server allows a connection, a wxConnection object will be
        returned. The type of wxConnection returned can be altered by
        overriding the
        OnMakeConnection()
        member to return your own derived connection object.
        Under Unix, the service name may be either an integer port
        identifier in which case an Internet domain socket will be used
        for the communications, or a valid file name (which shouldn't
        exist and will be deleted afterwards) in which case a Unix domain
        socket is created.
        @b SECURITY NOTE: Using Internet domain sockets if extremely
        insecure for IPC as there is absolutely no access control for
        them, use Unix domain sockets whenever possible!
    */
    wxConnectionBase* MakeConnection(const wxString& host,
                                     const wxString& service,
                                     const wxString& topic);

    /**
        Called by MakeConnection(), by
        default this simply returns a new wxConnection object. Override
        this method to return a wxConnection descendant customised for the
        application.
        The advantage of deriving your own connection class is that it
        will enable you to intercept messages initiated by the server,
        such as wxConnection::OnAdvise. You
        may also want to store application-specific data in instances of
        the new class.
    */
    wxConnectionBase* OnMakeConnection();

    /**
        Returns @true if this is a valid host name, @false otherwise. This always
        returns @true under MS Windows.
    */
    bool ValidHost(const wxString& host);
};


/**
    @class wxServer
    @wxheader{ipc.h}

    A wxServer object represents the server part of a client-server
    DDE-like (Dynamic Data Exchange) conversation. The actual
    DDE-based implementation using wxDDEServer is available on Windows
    only, but a platform-independent, socket-based version of this
    API is available using wxTCPServer, which has the same API.

    To create a server which can communicate with a suitable client,
    you need to derive a class from wxConnection and another from
    wxServer. The custom wxConnection class will intercept
    communications in a 'conversation' with a client, and the custom
    wxServer is required so that a user-overridden wxServer::OnAcceptConnection
    member can return a wxConnection of the required class, when a
    connection is made. Look at the IPC sample and the @ref overview_ipcoverview
    "Interprocess communications overview" for
    an example of how to do this.

    @library{wxbase}
    @category{FIXME}

    @seealso
    wxClient, wxConnection, IPC, overview
*/
class wxServer
{
public:
    /**
        Constructs a server object.
    */
    wxServer();

    /**
        Registers the server using the given service name. Under Unix,
        the service name may be either an integer port identifier in
        which case an Internet domain socket will be used for the
        communications, or a valid file name (which shouldn't exist and
        will be deleted afterwards) in which case a Unix domain socket is
        created. @false is returned if the call failed (for example, the
        port number is already in use).
    */
    bool Create(const wxString& service);

    /**
        When a client calls @b MakeConnection, the server receives the
        message and this member is called. The application should derive a
        member to intercept this message and return a connection object of
        either the standard wxConnection type, or (more likely) of a
        user-derived type.
        If the topic is @b STDIO, the application may wish to refuse the
        connection. Under UNIX, when a server is created the
        OnAcceptConnection message is always sent for standard input and
        output, but in the context of DDE messages it doesn't make a lot
        of sense.
    */
    virtual wxConnectionBase* OnAcceptConnection(const wxString& topic);
};