# Agent-side MIB implementations

## Implementing scalar MIB objects

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

- SNMPv2c

- with SNMP community “public”

- serving custom Managed Object Instance defined within this script

- allow read access only to the subtree where the custom MIB object resides

- over IPv4/UDP, listening at 127.0.0.1:161

- using Twisted fraework for network transport

Either of the following Net-SNMP commands will walk this Agent:

$ snmpwalk -v2c -c public 127.0.0.1 .1.3.6

    import sys
    from twisted.internet import reactor
    from pysnmp.entity import engine, config
    from pysnmp.entity.rfc3413 import cmdrsp, context
    from pysnmp.proto import rfc1902
    from pysnmp.carrier.twisted.dgram import udp

    # Create SNMP engine with autogenernated engineID and pre-bound
    # to socket transport dispatcher
    snmpEngine = engine.SnmpEngine()

    # Transport setup

    # UDP over IPv4
    config.addTransport(
        snmpEngine,
        udp.domainName,
        udp.UdpTwistedTransport().openServerMode(('127.0.0.1', 161))
    )

    # SNMPv2c setup

    # SecurityName <-> CommunityName mapping.
    config.addV1System(snmpEngine, 'my-area', 'public')

    # Allow read MIB access for this user / securityModels at VACM
    config.addVacmUser(snmpEngine, 2, 'my-area', 'noAuthNoPriv', (1, 3, 6, 5))

    # Create an SNMP context
    snmpContext = context.SnmpContext(snmpEngine)

    # --- create custom Managed Object Instance ---

    mibBuilder = snmpContext.getMibInstrum().getMibBuilder()

    MibScalar, MibScalarInstance = mibBuilder.importSymbols(
        'SNMPv2-SMI', 'MibScalar', 'MibScalarInstance'
    )

    class MyStaticMibScalarInstance(MibScalarInstance):
        # noinspection PyUnusedLocal,PyUnusedLocal
        def getValue(self, name, idx):
            return self.getSyntax().clone(
                'Python %s running on a %s platform' % (sys.version, sys.platform)
            )

    mibBuilder.exportSymbols(
        '__MY_MIB', MibScalar((1, 3, 6, 5, 1), rfc1902.OctetString()),
        MyStaticMibScalarInstance((1, 3, 6, 5, 1), (0,), rfc1902.OctetString())
    )

    # --- end of Managed Object Instance initialization ----

    # Register SNMP Applications at the SNMP engine for particular SNMP context
    cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
    cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
    cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

    # Run Twisted main loop
    reactor.run()

`Download` script.

See also: library reference.