Package org.snmp4j.mp
The org.snmp4j.mp
classes provide services to process SNMP
messages. The services provided are defined in the
MessageProcessingModel
interface and include the following:
- Prepare data elements from an incoming SNMP message as described in RFC3412 §7.2.
- Prepare a response message as defined in RFC3412 §7.1.
- Prepare an outgoing message as defined in RFC3412 §7.1.
This interface is implemented
by the message processing model classes for the SNMP versions 1, v2c, and v3:
MPv1
, MPv2c
, and MPv3
.
The MessageDispatcherImpl
chooses which message processing model
it uses to process an outgoing or incoming SNMP message based on the SNMP
version of the message. The SNMP version is either extracted from the message
header (incoming message) or from the Target
instance associated
with the outgoing PDU (ougoing message).
To be able to match requests and responses SNMP uses request IDs. Since request
IDs are created by the command generator, the request IDs are unique within
such a command generator only. SNMP4J therefore has to abstract from request IDs
and uses PduHandle
instances instead.
If a PDU
is processed for sending by the SNMP4J
MessageDispatcherImpl
and
the PDU's request ID is set to 0, then a SNMP4J application wide unique ID
is generated and set as request ID of the supplied PDU. In any case, the
PDU's request ID will be used as transaction ID of the outgoing message. The
transaction ID identifies a messages PduHandle
.
If a PDU
is received by the SNMP4J
MessageDispatcherImpl
a unique transaction ID is generated so
that command responders as well as the message processing model can match
requests and responses.
The following UML class diagram shows the most important classes of the
org.snmp4j.mp
package and their relationships
(relationships to other packages are not shown):
-
ClassDescriptionThe
CounterSupport
class provides support to fireCounterEvent
to registered listeners.TheDefaultCounterListener
is the default implementation of theCounterListener
interface.The interfaceEngineIdCacheSize
defines the maximum engine ID cache size when the cache size is about to increase.TheMessageID
interface defines the characteristics of a SNMP message ID as defined by RFC 3412 §6.2.TheMessageProcessingModel
interface defines common methods to all SNMP message processing models.TheMPv1
is the message processing model for SNMPv1.TheMPv2c
is the message processing model for SNMPv2c (community based SNMPv2).TheMPv3
is the message processing model for SNMPv3.TheCache
stores state reference information for the MPv3.MPv3.CacheEntry<A extends Address>TheCacheEntry
class holds state reference information for the MPv3 message processing model for a single message.TheEngineIdCacheFactory
creates an engine ID cache with upper limit.TheHeaderData
represents the message header information of SNMPv3 message.TheMutableStateReference
encapsulates aStateReference
for read/write access.ThePduHandle
class represents an unique key for a SNMP PDU.ThePduHandleCallback
can be used to get informed about aPduHandle
creation before a request is actually sent out.TheRequestStatistics
interface defines statistic values about request processing.TheSimpleMessageID
implements the simplest possibleMessageID
with a minimum memory footprint.TheSnmpConstants
class holds constants, ObjectIDs and Message strings used within SNMP4J.Enumeration of the textual convention StorageType defined in SNMPv2-TC MIB.StateReference<A extends Address>TheStateReference
class represents state information associated with SNMP messages.TheStatusInformation
class represents status information of a SNMPv3 message that is needed to return a report message.TheTimedMessageID
adds system time information to the message ID that allows to measure response times and detect lost messages with SNMPv3.