SNMPAPI_CALLBACK callback function (winsnmp.h)

Article
02/22/2024

[SNMP is available for use in the operating systems specified in the Requirements section. It may be altered or unavailable in subsequent versions. Instead, use Windows Remote Management, which is the Microsoft implementation of WS-Man.]

The Microsoft WinSNMP implementation calls the SNMPAPI_CALLBACK function to notify a WinSNMP session that an SNMP message or asynchronous event is available.

SNMPAPI_CALLBACK is a placeholder for an application- or library-defined callback function name.

Syntax

SNMPAPI_CALLBACK SnmpapiCallback;

SNMPAPI_STATUS SnmpapiCallback(
  [in] HSNMP_SESSION hSession,
  [in] HWND hWnd,
  [in] UINT wMsg,
  [in] WPARAM wParam,
  [in] LPARAM lParam,
  [in] LPVOID lpClientData
)
{...}

Parameters

[in] hSession

Handle to the WinSNMP session.

[in] hWnd

Handle to a window of the WinSNMP application to notify when an asynchronous request completes, or when trap notification occurs. This parameter does not have significance for the WinSNMP session, but the implementation always passes the value to the callback function.

[in] wMsg

Specifies an unsigned integer that identifies the notification message to send to the WinSNMP application window. This parameter does not have significance for the WinSNMP session, but the implementation always passes the value to the callback function.

[in] wParam

Specifies an application-defined 32-bit value that identifies the type of notification. If this parameter is equal to zero, an SNMP message is available for the session. The application should call the SnmpRecvMsg function to retrieve the message. If this parameter is not equal to zero, it indicates an asynchronous event notification for the session. For additional information, see the following Remarks section.

[in] lParam

Specifies an application-defined 32-bit value that specifies the request identifier of the PDU being processed.

[in] lpClientData

If the lpClientData parameter was not NULL on the call to the SnmpCreateSession function for this session, this parameter is a pointer to application-defined data.

Return value

The function must return SNMPAPI_SUCCESS to continue execution of the application. If the function returns any other value, the implementation responds as if the application called the SnmpClose function for the indicated session.

Remarks

When the implementation is executing the retransmission policy for the WinSNMP application and a transmission time-out occurs, the implementation informs the session of the error. In this situation the value of the wParam parameter would be SNMPAPI_TL_TIMEOUT. For a list of other transport layer errors, see the reference pages for the SnmpRegister, SnmpSendMsg, and SnmpRecvMsg functions.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winsnmp.h