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
  50         If the arguments of the wxConnection constructor are void then
  51         the wxConnection object manages its own connection buffer,
  52         allocating memory as needed. A programmer-supplied buffer cannot
  53         be increased if necessary, and the program will assert if it is
  54         not large enough. The programmer-supplied buffer is included
  55         mainly for backwards compatibility.
  56     */
  57     wxConnection();
  58     wxConnection(void* buffer, size_t size);
  59     //@}
  60
  61     //@{
  62     /**
  63         Called by the server application to advise the client of a change
  64         in the data associated with the given item. Causes the client
  65         connection's OnAdvise() member
  66         to be called. Returns @true if successful.
  67     */
  68     bool Advise(const wxString& item, const void* data, size_t size,
  69                 wxIPCFormat format = wxIPC_PRIVATE);
  70     bool Advise(const wxString& item, const char* data);
  71     bool Advise(const wxString& item, const wchar_t* data);
  72     bool Advise(const wxString& item, const wxString data);
  73     //@}
  74
  75     /**
  76         Called by the client or server application to disconnect from the
  77         other program; it causes the OnDisconnect()
  78         message to be sent to the corresponding connection object in the
  79         other program. Returns @true if successful or already disconnected.
  80         The application that calls @b Disconnect must explicitly delete
  81         its side of the connection.
  82     */
  83     bool Disconnect();
  84
  85     //@{
  86     /**
  87         Called by the client application to execute a command on the
  88         server. Can also be used to transfer arbitrary data to the server
  89         (similar to Poke() in
  90         that respect). Causes the server connection's OnExec()
  91         member to be called. Returns @true if successful.
  92     */
  93     bool Execute(const void* data, size_t size,
  94                  wxIPCFormat format = wxIPC_PRIVATE);
  95     bool Execute(const char* data);
  96     bool Execute(const wchar_t* data);
  97     bool Execute(const wxString data);
  98     //@}
  99
 100     /**
 101         Message sent to the client application when the server notifies
 102         it of a change in the data associated with the given item, using
 103         Advise().
 104     */
 105     virtual bool OnAdvise(const wxString& topic,
 106                           const wxString& item,
 107                           const void* data,
 108                           size_t size,
 109                           wxIPCFormat format);
 110
 111     /**
 112         Message sent to the client or server application when the other
 113         application notifies it to end the connection. The default
 114         behaviour is to delete the connection object and return @true, so
 115         applications should generally override @b OnDisconnect
 116         (finally calling the inherited method as well) so that they know
 117         the connection object is no longer available.
 118     */
 119     virtual bool OnDisconnect();
 120
 121     /**
 122         Message sent to the server application when the client notifies
 123         it to execute the given data, using Execute().
 124         Note that there is no item associated with this message.
 125     */
 126     virtual bool OnExec(const wxString& topic, const wxString& data);
 127
 128     /**
 129         Message sent to the server application when the client notifies it to
 130         accept the given data.
 131     */
 132     virtual bool OnPoke(const wxString& topic, const wxString& item,
 133                         const void* data,
 134                         size_t size,
 135                         wxIPCFormat format);
 136
 137     /**
 138         Message sent to the server application when the client calls
 139         Request(). The
 140         server's OnRequest() method
 141         should respond by returning a character string, or @NULL to
 142         indicate no data, and setting *size. The character string must of
 143         course persist after the call returns.
 144     */
 145     virtual const void* OnRequest(const wxString& topic,
 146                                   const wxString& item,
 147                                   size_t * size,
 148                                   wxIPCFormat format);
 149
 150     /**
 151         Message sent to the server application by the client, when the client
 152         wishes to start an 'advise loop' for the given topic and item. The
 153         server can refuse to participate by returning @false.
 154     */
 155     virtual bool OnStartAdvise(const wxString& topic,
 156                                const wxString& item);
 157
 158     /**
 159         Message sent to the server application by the client, when the client
 160         wishes to stop an 'advise loop' for the given topic and item. The
 161         server can refuse to stop the advise loop by returning @false, although
 162         this doesn't have much meaning in practice.
 163     */
 164     virtual bool OnStopAdvise(const wxString& topic,
 165                               const wxString& item);
 166
 167     //@{
 168     /**
 169         Called by the client application to poke data into the server.
 170         Can be used to transfer arbitrary data to the server. Causes the
 171         server connection's OnPoke() member to
 172         be called. If size is -1 the size is computed from the string
 173         length of data.
 174
 175         Returns @true if successful.
 176     */
 177     bool Poke(const wxString& item, const void* data, size_t size,
 178               wxIPCFormat format = wxIPC_PRIVATE);
 179     bool Poke(const wxString& item, const char* data);
 180     bool Poke(const wxString& item, const wchar_t* data);
 181     bool Poke(const wxString& item, const wxString data);
 182     //@}
 183
 184     /**
 185         Called by the client application to request data from the server.
 186         Causes the server connection's OnRequest()
 187         member to be called. Size may be @NULL or a pointer to a variable
 188         to receive the size of the requested item.
 189
 190         Returns a character string (actually a pointer to the
 191         connection's buffer) if successful, @NULL otherwise. This buffer
 192         does not need to be deleted.
 193     */
 194     const void* Request(const wxString& item, size_t * size,
 195                         wxIPCFormat format = wxIPC_TEXT);
 196
 197     /**
 198         Called by the client application to ask if an advise loop can be
 199         started with the server. Causes the server connection's
 200         OnStartAdvise()
 201         member to be called. Returns @true if the server okays it, @false
 202         otherwise.
 203     */
 204     bool StartAdvise(const wxString& item);
 205
 206     /**
 207         Called by the client application to ask if an advise loop can be
 208         stopped. Causes the server connection's OnStopAdvise()
 209         member to be called. Returns @true if the server okays it, @false
 210         otherwise.
 211     */
 212     bool StopAdvise(const wxString& item);
 213 };
 214
 215
 216 /**
 217     @class wxClient
 218     @wxheader{ipc.h}
 219
 220     A wxClient object represents the client part of a client-server
 221     DDE-like (Dynamic Data Exchange) conversation. The actual
 222     DDE-based implementation using wxDDEClient is available on Windows
 223     only, but a platform-independent, socket-based version of this
 224     API is available using wxTCPClient, which has the same API.
 225
 226     To create a client which can communicate with a suitable server,
 227     you need to derive a class from wxConnection and another from
 228     wxClient. The custom wxConnection class will intercept
 229     communications in a 'conversation' with a server, and the custom
 230     wxClient is required so that a user-overridden
 231     wxClient::OnMakeConnection
 232     member can return a wxConnection of the required class, when a
 233     connection is made. Look at the IPC sample and the
 234     @ref overview_ipcoverview "Interprocess communications overview" for
 235     an example of how to do this.
 236
 237     @library{wxbase}
 238     @category{FIXME}
 239
 240     @seealso
 241     wxServer, wxConnection, @ref overview_ipcoverview "Interprocess communications
 242     overview"
 243 */
 244 class wxClient : public wxObject
 245 {
 246 public:
 247     /**
 248         Constructs a client object.
 249     */
 250     wxClient();
 251
 252     /**
 253         Tries to make a connection with a server by host (machine name
 254         under UNIX - use 'localhost' for same machine; ignored when using
 255         native DDE in Windows), service name and topic string. If the
 256         server allows a connection, a wxConnection object will be
 257         returned. The type of wxConnection returned can be altered by
 258         overriding the
 259         OnMakeConnection()
 260         member to return your own derived connection object.
 261
 262         Under Unix, the service name may be either an integer port
 263         identifier in which case an Internet domain socket will be used
 264         for the communications, or a valid file name (which shouldn't
 265         exist and will be deleted afterwards) in which case a Unix domain
 266         socket is created.
 267
 268         @b SECURITY NOTE: Using Internet domain sockets if extremely
 269         insecure for IPC as there is absolutely no access control for
 270         them, use Unix domain sockets whenever possible!
 271     */
 272     wxConnectionBase * MakeConnection(const wxString& host,
 273                                       const wxString& service,
 274                                       const wxString& topic);
 275
 276     /**
 277         Called by MakeConnection(), by
 278         default this simply returns a new wxConnection object. Override
 279         this method to return a wxConnection descendant customised for the
 280         application.
 281
 282         The advantage of deriving your own connection class is that it
 283         will enable you to intercept messages initiated by the server,
 284         such as wxConnection::OnAdvise. You
 285         may also want to store application-specific data in instances of
 286         the new class.
 287     */
 288     wxConnectionBase * OnMakeConnection();
 289
 290     /**
 291         Returns @true if this is a valid host name, @false otherwise. This always
 292         returns @true under MS Windows.
 293     */
 294     bool ValidHost(const wxString& host);
 295 };
 296
 297
 298 /**
 299     @class wxServer
 300     @wxheader{ipc.h}
 301
 302     A wxServer object represents the server part of a client-server
 303     DDE-like (Dynamic Data Exchange) conversation. The actual
 304     DDE-based implementation using wxDDEServer is available on Windows
 305     only, but a platform-independent, socket-based version of this
 306     API is available using wxTCPServer, which has the same API.
 307
 308     To create a server which can communicate with a suitable client,
 309     you need to derive a class from wxConnection and another from
 310     wxServer. The custom wxConnection class will intercept
 311     communications in a 'conversation' with a client, and the custom
 312     wxServer is required so that a user-overridden wxServer::OnAcceptConnection
 313     member can return a wxConnection of the required class, when a
 314     connection is made. Look at the IPC sample and the @ref overview_ipcoverview
 315     "Interprocess communications overview" for
 316     an example of how to do this.
 317
 318     @library{wxbase}
 319     @category{FIXME}
 320
 321     @seealso
 322     wxClient, wxConnection, IPC, overview
 323 */
 324 class wxServer
 325 {
 326 public:
 327     /**
 328         Constructs a server object.
 329     */
 330     wxServer();
 331
 332     /**
 333         Registers the server using the given service name. Under Unix,
 334         the service name may be either an integer port identifier in
 335         which case an Internet domain socket will be used for the
 336         communications, or a valid file name (which shouldn't exist and
 337         will be deleted afterwards) in which case a Unix domain socket is
 338         created. @false is returned if the call failed (for example, the
 339         port number is already in use).
 340     */
 341     bool Create(const wxString& service);
 342
 343     /**
 344         When a client calls @b MakeConnection, the server receives the
 345         message and this member is called. The application should derive a
 346         member to intercept this message and return a connection object of
 347         either the standard wxConnection type, or (more likely) of a
 348         user-derived type.
 349
 350         If the topic is @b STDIO, the application may wish to refuse the
 351         connection. Under UNIX, when a server is created the
 352         OnAcceptConnection message is always sent for standard input and
 353         output, but in the context of DDE messages it doesn't make a lot
 354         of sense.
 355     */
 356     virtual wxConnectionBase * OnAcceptConnection(const wxString& topic);
 357 };