SnmpRegister function (winsnmp.h)

Article
10/13/2021

[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 WinSNMP SnmpRegister function registers or unregisters a WinSNMP application for trap and notification reception. The application can register and receive traps and notifications, or unregister and disable traps and notifications.

A WinSNMP application can register or unregister for one type of trap or notification, or for all traps and notifications, depending on the value of the notification parameter.

Syntax

SNMPAPI_STATUS SNMPAPI_CALL SnmpRegister(
  [in] HSNMP_SESSION session,
  [in] HSNMP_ENTITY  srcEntity,
  [in] HSNMP_ENTITY  dstEntity,
  [in] HSNMP_CONTEXT context,
  [in] smiLPCOID     notification,
  [in] smiUINT32     state
);

Parameters

[in] session

Handle to the WinSNMP session that is registering or unregistering for traps and notifications.

[in] srcEntity

Handle to the management entity that is the source of the registration request. This entity, acting in an SNMP manager role, will receive the trap or notification.

Because the implementation does not use this parameter to filter traps and notifications from reaching the WinSNMP application, a WinSNMP manager application typically passes NULL in this parameter.

If this parameter is NULL, the Microsoft WinSNMP implementation registers or unregisters all sources of trap and notification requests.

Note that the srcEntity parameter to the SnmpRecvMsg function has a different role. In that function, srcEntity receives a handle to the entity that sent the trap.

[in] dstEntity

Handle to the management entity that is the recipient of the registration request. This entity, acting in an SNMP agent role, will send the trap or notification.

If this parameter is NULL, the implementation registers or unregisters the WinSNMP application for traps and notifications from all management entities.

Note that the dstEntity parameter to the SnmpRecvMsg function receives a handle to the management entity that registers for trap notification.

[in] context

Handle to the context, which is a set of managed object resources.

If this parameter is NULL, the implementation registers or unregisters the WinSNMP application for traps and notifications for every context.

[in] notification

Pointer to an smiOID structure that contains the pattern-matching sequence for one type of trap or notification. The implementation uses this sequence to identify the type of trap or notification for which the WinSNMP application is registering or unregistering. For additional information, see the following Remarks section.

If this parameter is NULL, the implementation registers or unregisters the WinSNMP application for all traps and notifications from the management entity or entities specified by the dstEntity parameter.

[in] state

Specifies an unsigned long integer variable that indicates whether the WinSNMP application is registering to receive traps and notifications, or if it is unregistering. This parameter should be equal to one of the following values, but if it contains a different value, the implementation registers the application.

Value	Meaning
SNMPAPI_OFF	Disable traps and notifications.
SNMPAPI_ON	Register to receive traps and notifications.

Return value

If the function succeeds, the return value is SNMPAPI_SUCCESS.

If the function fails, the return value is SNMPAPI_FAILURE. To get extended error information, call SnmpGetLastError. The SnmpGetLastError function may return one of the following WinSNMP or network transport layer errors.

Return code	Description
SNMPAPI_NOT_INITIALIZED	The SnmpStartup function did not complete successfully.
SNMPAPI_ALLOC_ERROR	An error occurred during memory allocation.
SNMPAPI_SESSION_INVALID	The session parameter is invalid.
SNMPAPI_ENTITY_INVALID	One or both of the entity parameters is invalid.
SNMPAPI_CONTEXT_INVALID	The context parameter is invalid.
SNMPAPI_OID_INVALID	The notification parameter is invalid.
SNMPAPI_TL_NOT_INITIALIZED	The network transport layer was not initialized, or the SNMPTRAP.EXE service could not be started.
SNMPAPI_TL_IN_USE	The trap port is not available.
SNMPAPI_TL_NOT_AVAILABLE	The network subsystem failed.
SNMPAPI_OTHER_ERROR	An unknown or undefined error occurred.

For additional information, see Network Transport Errors.

Remarks

Typically a WinSNMP manager application, rather than an agent application, calls the SnmpRegister function.

It is important to note that for users who are not administrators, the SnmpRegister function succeeds on Windows 2000 and Windows XP only if the SNMP trap service has been started.

If a WinSNMP application passes NULL in a call to the SnmpRegister function in the srcEntity, dstEntity, context, or notification parameters, the implementation does not use that parameter to filter traps and notifications from reaching the WinSNMP application. If an application passes NULL in all of the parameters mentioned previously, the implementation delivers all received notifications to the session.

If a WinSNMP application registers to receive a specific type of trap or notification, it must define an object identifier, that is, an smiOID structure, that corresponds to that type of trap. The notification parameter must point to this structure. RFC 1907, "Management Information Base for Version 2 of the Simple Network Management Protocol (SNMPv2)," defines trap and notification object identifiers. For additional information, see Managing Traps and Notifications and Translating Traps from SNMPv1 to SNMPv2C.

The implementation uses the value of the notification parameter as a pattern to match against received traps and notifications. For example, if the WinSNMP application passes n number of subidentifiers in the notification parameter, and the first n subidentifiers in a received trap match all the passed subidentifiers, then the trap object identifier is a match. If a received trap has fewer subidentifiers than n, the object identifier does not match. If there is a match, the implementation sends the trap or notification to the WinSNMP application.

If any or all of the dstEntity, srcEntity, or context parameters are NULL, the implementation may need to allocate resources on a subsequent call to the SnmpRecvMsg function, for that function's corresponding parameters. When the WinSNMP application no longer needs the resources SnmpRecvMsg returns, the application must free the individual resources with the function that corresponds to the resource. For additional information, see SnmpFreeEntity and SnmpFreeContext.

For more information, see Multiple Trap Registrations.

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
Library	Wsnmp32.lib
DLL	Wsnmp32.dll