Using Lobby Messages

Lobby messages fall into two categories: DirectPlay-defined messages and application-defined messages.

DirectPlay-defined messages can be system messages, generated automatically by DirectPlay and sent to the lobby to inform it of changes in the status of the application, or standard message types, sent from the application to the lobby or from the lobby to the application.

The advantage of standard messages over application-defined messages is that the receiver can always interpret a standard message. A lobby client is not necessarily going to be able to handle custom messages from an application, just as an application may not be able to handle custom messages from a lobby client.

[C++]

Lobby messages are retrieved by using the IDirectPlayLobby3::ReceiveLobbyMessage method. The message category can be identified by the value returned in the variable pointed to by the lpdwMessageFlags parameter. If neither DPLMSG_SYSTEM or DPLMSG_STANDARD is present, the message is application-defined.

Lobbies should be prepared to handle all the standard message types. If an application uses the DPLMSG_GETPROPERTY message, it must be able to handle DPLMSG_GETPROPERTYRESPONSE messages. (See Staying in Touch with the Lobby.)

DirectPlay-defined messages all start with a DWORD value that identifies the message type. After retrieving a message using ReceiveLobbyMessage, cast *lpData to the DPLMSG_GENERIC structure and examine the structure's dwType member. Then cast *lpData to the appropriate message structure for further processing.

The following table shows the possible values of DPLMSG_GENERIC.dwType for standard messages, and the structure and message cause associated with each value.

Value of dwType	Message structure	Cause
DPLSYS _APPTERMINATED	DPLMSG_SYSTEMMESSAGE	The application has terminated.
DPLSYS _CONNECTIONSETTINGSREAD	DPLMSG_SYSTEMMESSAGE	The application has read the connection settings.
DPLSYS _DPLAYCONNECTFAILED	DPLMSG_SYSTEMMESSAGE	The application failed to connect to the DirectPlay session.
DPLSYS _DPLAYCONNECTSUCCEEDED	DPLMSG_SYSTEMMESSAGE	The application successfully connected to the DirectPlay session.
DPLSYS _GETPROPERTY	DPLMSG_GETPROPERTY	The application is requesting a property from the lobby. See Staying in Touch with the Lobby.
DPLSYS _GETPROPERTYRESPONSE	DPLMSG_GETPROPERTYRESPONSE	The lobby is responding to a DPLMSG_GETPROPERTY message. See Staying in Touch with the Lobby.
DPLSYS _NEWCONNECTIONSETTINGS	DPLMSG_SYSTEMMESSAGE	A waiting application was found when a lobby client called RunApplication. See Supporting Dynamic Lobby Connection.
DPLSYS _NEWSESSIONHOST	DPLMSG_NEWSESSIONHOST	The application session has a new host.
DPLSYS _SETPROPERTY	DPLMSG_SETPROPERTY	The application is setting a property on the lobby. See Staying in Touch with the Lobby.
DPLSYS _SETPROPERTYRESPONSE	DPLMSG_SETPROPERTYRESPONSE	The lobby is responding to a DPLMSG_SETPROPERTY message. See Staying in Touch with the Lobby.

[Visual Basic]

Lobby messages are retrieved by using the DirectPlayLobby3.ReceiveLobbyMessage method. The message category can be identified by the value returned in the messageFlags parameter. If neither DPLMSG_SYSTEM or DPLMSG_STANDARD is present, the message is application-defined.

Lobbies should be prepared to handle all the standard message types. If an application uses the DPLSYS_GETPROPERTY message, it must be able to handle DPLSYS_GETPROPERTYRESPONSE messages. (See Staying in Touch with the Lobby.)

DirectPlay-defined messages all start with a value from the CONST_DPSYSMSGTYPES enumeration that identifies the message type. You retrieve this value by using DirectPlayMessage.ReadLong.

The following table shows the message type and the message cause associated with each value.

Message Type	Cause
DPLSYS _APPTERMINATED	The application has terminated.
DPLSYS _CONNECTIONSETTINGSREAD	The application has read the connection settings.
DPLSYS _DPLAYCONNECTFAILED	The application failed to connect to the DirectPlay session.
DPLSYS _DPLAYCONNECTSUCCEEDED	The application successfully connected to the DirectPlay session.
DPLSYS _GETPROPERTY	The application is requesting a property from the lobby. See Staying in Touch with the Lobby.
DPLSYS _GETPROPERTYRESPONSE	The lobby is responding to a DPLMSG_GETPROPERTY message. See Staying in Touch with the Lobby.
DPLSYS _NEWCONNECTIONSETTINGS	A waiting application was found when a lobby client called RunApplication. See Supporting Dynamic Lobby Connection.
DPLSYS _NEWSESSIONHOST	The application session has a new host.
DPLSYS _SETPROPERTY	The application is setting a property on the lobby. See Staying in Touch with the Lobby.
DPLSYS _SETPROPERTYRESPONSE	The lobby is responding to a DPLMSG_SETPROPERTY message. See Staying in Touch with the Lobby.