interface/ipc.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        ipc.h
   3 // Purpose:     documentation for wxConnection class
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxConnection
  11     @wxheader{ipc.h}
  12
  13     A wxConnection object represents the connection between a client
  14     and a server. It is created by making a connection using a
  15     wxClient object, or by the acceptance of a
  16     connection by a wxServer object. The
  17     bulk of a DDE-like (Dynamic Data Exchange) conversation is
  18     controlled by calling members in a @b wxConnection object or
  19     by overriding its members. The actual DDE-based implementation
  20     using wxDDEConnection is available on Windows only, but a
  21     platform-independent, socket-based version of this API is
  22     available using wxTCPConnection, which has the same API.
  23
  24     An application should normally derive a new connection class from
  25     wxConnection, in order to override the communication event
  26     handlers to do something interesting.
  27
  28     @library{wxbase}
  29     @category{FIXME}
  30
  31     @seealso
  32     wxClient, wxServer, @ref overview_ipcoverview "Interprocess communications
  33     overview"
  34 */
  35 class wxConnection : public wxObject
  36 {
  37 public:
  38     //@{
  39     /**
  40         Constructs a connection object. If no user-defined connection
  41         object is to be derived from wxConnection, then the constructor
  42         should not be called directly, since the default connection
  43         object will be provided on requesting (or accepting) a
  44         connection. However, if the user defines his or her own derived
  45         connection object, the wxServer::OnAcceptConnection
  46         and/or wxClient::OnMakeConnection
  47         members should be replaced by functions which construct the new
  48         connection object.
  49         If the arguments of the wxConnection constructor are void then
  50         the wxConnection object manages its own connection buffer,
  51         allocating memory as needed. A programmer-supplied buffer cannot
  52         be increased if necessary, and the program will assert if it is
  53         not large enough. The programmer-supplied buffer is included
  54         mainly for backwards compatibility.
  55     */
  56     wxConnection();
  57     wxConnection(void* buffer, size_t size);
  58     //@}
  59
  60     //@{
  61     /**
  62         Called by the server application to advise the client of a change
  63         in the data associated with the given item. Causes the client
  64         connection's OnAdvise() member
  65         to be called. Returns @true if successful.
  66     */
  67     bool Advise(const wxString& item, const void* data, size_t size,
  68                 wxIPCFormat format = wxIPC_PRIVATE);
  69     bool Advise(const wxString& item, const char* data);
  70     bool Advise(const wxString& item, const wchar_t* data);
  71     bool Advise(const wxString& item, const wxString data);
  72     //@}
  73
  74     /**
  75         Called by the client or server application to disconnect from the
  76         other program; it causes the OnDisconnect()
  77         message to be sent to the corresponding connection object in the
  78         other program. Returns @true if successful or already disconnected.
  79         The application that calls @b Disconnect must explicitly delete
  80         its side of the connection.
  81     */
  82     bool Disconnect();
  83
  84     //@{
  85     /**
  86         Called by the client application to execute a command on the
  87         server. Can also be used to transfer arbitrary data to the server
  88         (similar to Poke() in
  89         that respect). Causes the server connection's OnExec()
  90         member to be called. Returns @true if successful.
  91     */
  92     bool Execute(const void* data, size_t size,
  93                  wxIPCFormat format = wxIPC_PRIVATE);
  94     bool Execute(const char* data);
  95     bool Execute(const wchar_t* data);
  96     bool Execute(const wxString data);
  97     //@}
  98
  99     /**
 100         Message sent to the client application when the server notifies
 101         it of a change in the data associated with the given item, using
 102         Advise().
 103     */
 104     virtual bool OnAdvise(const wxString& topic,
 105                           const wxString& item,
 106                           const void* data,
 107                           size_t size,
 108                           wxIPCFormat format);
 109
 110     /**
 111         Message sent to the client or server application when the other
 112         application notifies it to end the connection. The default
 113         behaviour is to delete the connection object and return @true, so
 114         applications should generally override @b OnDisconnect
 115         (finally calling the inherited method as well) so that they know
 116         the connection object is no longer available.
 117     */
 118     virtual bool OnDisconnect();
 119
 120     /**
 121         Message sent to the server application when the client notifies
 122         it to execute the given data, using Execute().
 123         Note that there is no item associated with this message.
 124     */
 125     virtual bool OnExec(const wxString& topic, const wxString& data);
 126
 127     /**
 128         Message sent to the server application when the client notifies it to
 129         accept the given data.
 130     */
 131     virtual bool OnPoke(const wxString& topic, const wxString& item,
 132                         const void* data,
 133                         size_t size,
 134                         wxIPCFormat format);
 135
 136     /**
 137         Message sent to the server application when the client calls
 138         Request(). The
 139         server's OnRequest() method
 140         should respond by returning a character string, or @NULL to
 141         indicate no data, and setting *size. The character string must of
 142         course persist after the call returns.
 143     */
 144     virtual const void* OnRequest(const wxString& topic,
 145                                   const wxString& item,
 146                                   size_t* size,
 147                                   wxIPCFormat format);
 148
 149     /**
 150         Message sent to the server application by the client, when the client
 151         wishes to start an 'advise loop' for the given topic and item. The
 152         server can refuse to participate by returning @false.
 153     */
 154     virtual bool OnStartAdvise(const wxString& topic,
 155                                const wxString& item);
 156
 157     /**
 158         Message sent to the server application by the client, when the client
 159         wishes to stop an 'advise loop' for the given topic and item. The
 160         server can refuse to stop the advise loop by returning @false, although
 161         this doesn't have much meaning in practice.
 162     */
 163     virtual bool OnStopAdvise(const wxString& topic,
 164                               const wxString& item);
 165
 166     //@{
 167     /**
 168         Called by the client application to poke data into the server.
 169         Can be used to transfer arbitrary data to the server. Causes the
 170         server connection's OnPoke() member to
 171         be called. If size is -1 the size is computed from the string
 172         length of data.
 173         Returns @true if successful.
 174     */
 175     bool Poke(const wxString& item, const void* data, size_t size,
 176               wxIPCFormat format = wxIPC_PRIVATE);
 177     bool Poke(const wxString& item, const char* data);
 178     bool Poke(const wxString& item, const wchar_t* data);
 179     bool Poke(const wxString& item, const wxString data);
 180     //@}
 181
 182     /**
 183         Called by the client application to request data from the server.
 184         Causes the server connection's OnRequest()
 185         member to be called. Size may be @NULL or a pointer to a variable
 186         to receive the size of the requested item.
 187         Returns a character string (actually a pointer to the
 188         connection's buffer) if successful, @NULL otherwise. This buffer
 189         does not need to be deleted.
 190     */
 191     const void* Request(const wxString& item, size_t* size,
 192                         wxIPCFormat format = wxIPC_TEXT);
 193
 194     /**
 195         Called by the client application to ask if an advise loop can be
 196         started with the server. Causes the server connection's
 197         OnStartAdvise()
 198         member to be called. Returns @true if the server okays it, @false
 199         otherwise.
 200     */
 201     bool StartAdvise(const wxString& item);
 202
 203     /**
 204         Called by the client application to ask if an advise loop can be
 205         stopped. Causes the server connection's OnStopAdvise()
 206         member to be called. Returns @true if the server okays it, @false
 207         otherwise.
 208     */
 209     bool StopAdvise(const wxString& item);
 210 };
 211
 212
 213 /**
 214     @class wxClient
 215     @wxheader{ipc.h}
 216
 217     A wxClient object represents the client part of a client-server
 218     DDE-like (Dynamic Data Exchange) conversation. The actual
 219     DDE-based implementation using wxDDEClient is available on Windows
 220     only, but a platform-independent, socket-based version of this
 221     API is available using wxTCPClient, which has the same API.
 222
 223     To create a client which can communicate with a suitable server,
 224     you need to derive a class from wxConnection and another from
 225     wxClient. The custom wxConnection class will intercept
 226     communications in a 'conversation' with a server, and the custom
 227     wxClient is required so that a user-overridden
 228     wxClient::OnMakeConnection
 229     member can return a wxConnection of the required class, when a
 230     connection is made. Look at the IPC sample and the
 231     @ref overview_ipcoverview "Interprocess communications overview" for
 232     an example of how to do this.
 233
 234     @library{wxbase}
 235     @category{FIXME}
 236
 237     @seealso
 238     wxServer, wxConnection, @ref overview_ipcoverview "Interprocess communications
 239     overview"
 240 */
 241 class wxClient : public wxObject
 242 {
 243 public:
 244     /**
 245         Constructs a client object.
 246     */
 247     wxClient();
 248
 249     /**
 250         Tries to make a connection with a server by host (machine name
 251         under UNIX - use 'localhost' for same machine; ignored when using
 252         native DDE in Windows), service name and topic string. If the
 253         server allows a connection, a wxConnection object will be
 254         returned. The type of wxConnection returned can be altered by
 255         overriding the
 256         OnMakeConnection()
 257         member to return your own derived connection object.
 258         Under Unix, the service name may be either an integer port
 259         identifier in which case an Internet domain socket will be used
 260         for the communications, or a valid file name (which shouldn't
 261         exist and will be deleted afterwards) in which case a Unix domain
 262         socket is created.
 263         @b SECURITY NOTE: Using Internet domain sockets if extremely
 264         insecure for IPC as there is absolutely no access control for
 265         them, use Unix domain sockets whenever possible!
 266     */
 267     wxConnectionBase* MakeConnection(const wxString& host,
 268                                      const wxString& service,
 269                                      const wxString& topic);
 270
 271     /**
 272         Called by MakeConnection(), by
 273         default this simply returns a new wxConnection object. Override
 274         this method to return a wxConnection descendant customised for the
 275         application.
 276         The advantage of deriving your own connection class is that it
 277         will enable you to intercept messages initiated by the server,
 278         such as wxConnection::OnAdvise. You
 279         may also want to store application-specific data in instances of
 280         the new class.
 281     */
 282     wxConnectionBase* OnMakeConnection();
 283
 284     /**
 285         Returns @true if this is a valid host name, @false otherwise. This always
 286         returns @true under MS Windows.
 287     */
 288     bool ValidHost(const wxString& host);
 289 };
 290
 291
 292 /**
 293     @class wxServer
 294     @wxheader{ipc.h}
 295
 296     A wxServer object represents the server part of a client-server
 297     DDE-like (Dynamic Data Exchange) conversation. The actual
 298     DDE-based implementation using wxDDEServer is available on Windows
 299     only, but a platform-independent, socket-based version of this
 300     API is available using wxTCPServer, which has the same API.
 301
 302     To create a server which can communicate with a suitable client,
 303     you need to derive a class from wxConnection and another from
 304     wxServer. The custom wxConnection class will intercept
 305     communications in a 'conversation' with a client, and the custom
 306     wxServer is required so that a user-overridden wxServer::OnAcceptConnection
 307     member can return a wxConnection of the required class, when a
 308     connection is made. Look at the IPC sample and the @ref overview_ipcoverview
 309     "Interprocess communications overview" for
 310     an example of how to do this.
 311
 312     @library{wxbase}
 313     @category{FIXME}
 314
 315     @seealso
 316     wxClient, wxConnection, IPC, overview
 317 */
 318 class wxServer
 319 {
 320 public:
 321     /**
 322         Constructs a server object.
 323     */
 324     wxServer();
 325
 326     /**
 327         Registers the server using the given service name. Under Unix,
 328         the service name may be either an integer port identifier in
 329         which case an Internet domain socket will be used for the
 330         communications, or a valid file name (which shouldn't exist and
 331         will be deleted afterwards) in which case a Unix domain socket is
 332         created. @false is returned if the call failed (for example, the
 333         port number is already in use).
 334     */
 335     bool Create(const wxString& service);
 336
 337     /**
 338         When a client calls @b MakeConnection, the server receives the
 339         message and this member is called. The application should derive a
 340         member to intercept this message and return a connection object of
 341         either the standard wxConnection type, or (more likely) of a
 342         user-derived type.
 343         If the topic is @b STDIO, the application may wish to refuse the
 344         connection. Under UNIX, when a server is created the
 345         OnAcceptConnection message is always sent for standard input and
 346         output, but in the context of DDE messages it doesn't make a lot
 347         of sense.
 348     */
 349     virtual wxConnectionBase* OnAcceptConnection(const wxString& topic);
 350 };