Open Client Client-Library/C Reference Manual

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Open Client Client-Library/C Reference Manual

Chapter 2 Topics

Callbacks

Server message callbacks

Defining a server message callback

A server message callback is defined as follows:

CS_RETCODE CS_PUBLIC 
 servermsg_cb(context, connection, message)
 
 CS_CONTEXT           *context;
 CS_CONNECTION    *connection;
 CS_SERVERMSG      *message;

where:

context is a pointer to the CS_CONTEXT structure for which the message occurred.
connection is a pointer to the CS_CONNECTION structure for which the message occurred.
message is a pointer to a CS_SERVERMSG structure containing server message information. For information on this structure, see the "CS_SERVERMSG structure".
Note that message can have a new value each time the server message callback is called.
A server message callback must return CS_SUCCEED.

Routines that a server message callback can call
Callable routines	Permitted use
ct_config	To retrieve information only.
ct_con_props	To retrieve information or to set the CS_USERDATA property only.
ct_cmd_props	To retrieve information only. The CS_USERDATA property can be set on command structures allocated with ct_cmd_alloc. The CS_USERDATA property cannot be set on the command structure obtained by the callback's ct_con_props(CS_EED_CMD) call.
ct_cancel(CS_CANCEL_ATTN)	Any circumstances.
ct_bind, ct_describe, ct_fetch, ct_get_data, ct_res_info	The routines must be called with the command structure returned by the callback's ct_con_props(CS_EED_CMD) call. A server message callback calls these routines only while extended error data is available; that is, until ct_fetch returns CS_END_DATA. See "Extended error data".

Warning!

Do not call ct_poll from within any Client-Library callback function or from within any other function that can execute at the system-interrupt level.

Calling ct_poll at the system-interrupt level can corrupt Open Client/Server internal resources and cause recursion in the application.


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