# Asynchronous: trollius

In order to use `asyncio` features with older Python (2.6+), you could download and install Trollius module. PySNMP’s asyncio bindings will work with Trollius as well.

In most examples approximate analogues of well known Net-SNMP snmp* tools command line options are shown. That may help those readers who, by chance are familiar with Net-SNMP tools, better understanding what example code doe

Here’s a quick example on a simple SNMP GET by high-level API:

> - with SNMPv1, community ‘public’

> - over IPv4/UDP

> - to an Agent at demo.snmplabs.com:161

> - for an instance of SNMPv2-MIB::sysDescr.0 MIB object

> - Based on trollius I/O framework

    import trollius
    from pysnmp.hlapi.asyncio import *

    @trollius.coroutine
    def run():
        snmpEngine = SnmpEngine()
        (errorIndication,
         errorStatus,
         errorIndex,
         varBinds) = yield trollius.From(
            getCmd(snmpEngine,
                   CommunityData('public', mpModel=0),
                   UdpTransportTarget(('demo.snmplabs.com', 161)),
                   ContextData(),
                   ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
        )

        if errorIndication:
            print(errorIndication)
        elif errorStatus:
            print('%s at %s' % (errorStatus.prettyPrint(),
                                errorIndex and varBinds[int(errorIndex) - 1][0] or '?'))
        else:
            for varBind in varBinds:
                print(' = '.join([x.prettyPrint() for x in varBind]))

        snmpEngine.transportDispatcher.closeDispatcher()

    trollius.get_event_loop().run_until_complete(run())

To make use of SNMPv3 and USM, the following code performs a series of SNMP GETNEXT operations effectively fetching a table of SNMP variables from SNMP Agent:

- with SNMPv3, user ‘usr-none-none’, no authentication, no privacy

- over IPv4/UDP

- to an Agent at demo.snmplabs.com:161

- for all OIDs past SNMPv2-MIB::system

- run till end-of-mib condition is reported by Agent

- based on trollius I/O framework

    import trollius
    from pysnmp.hlapi.asyncio import *

    @trollius.coroutine
    def run(varBinds):
        snmpEngine = SnmpEngine()
        while True:
            (errorIndication,
             errorStatus,
             errorIndex,
             varBindTable) = yield trollius.From(
                bulkCmd(snmpEngine,
                        UsmUserData('usr-none-none'),
                        UdpTransportTarget(('demo.snmplabs.com', 161)),
                        ContextData(),
                        0, 50,
                        *varBinds)
            )

            if errorIndication:
                print(errorIndication)
                break
            elif errorStatus:
                print('%s at %s' % (errorStatus.prettyPrint(),
                                    errorIndex and varBinds[int(errorIndex) - 1][0] or '?'))
            else:
                for varBindRow in varBindTable:
                    for varBind in varBindRow:
                        print(' = '.join([x.prettyPrint() for x in varBind]))

            varBinds = varBindTable[-1]
            if isEndOfMib(varBinds):
                break

        snmpEngine.transportDispatcher.closeDispatcher()

    loop = trollius.get_event_loop()

    loop.run_until_complete(
        run([ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr'))])
    )

More examples on Command Generator API usage follow.

- Various SNMP versions
  - SNMPv1
  - Bulk walk MIB
- Walking operations
  - Bulk walk MIB

Sending SNMP TRAP’s and INFORM’s is as easy with PySNMP library. The following code sends SNMP TRAP:

- SNMPv1

- with community name ‘public’

- over IPv4/UDP

- send TRAP notification

- with Generic Trap #1 (warmStart) and Specific Trap 0

- with default Uptime

- with default Agent Address

- with Enterprise OID 1.3.6.1.4.1.20408.4.1.1.2

- include managed object information ‘1.3.6.1.2.1.1.1.0’ = ‘my system’

- use trollius I/O framework

    import trollius
    from pysnmp.hlapi.asyncio import *

    @trollius.coroutine
    def run():
        snmpEngine = SnmpEngine()
        (errorIndication,
         errorStatus,
         errorIndex,
         varBinds) = yield trollius.From(
            sendNotification(
                snmpEngine,
                CommunityData('public'),  # mpModel=0),
                UdpTransportTarget(('demo.snmplabs.com', 162)),
                ContextData(),
                'inform',
                NotificationType(
                    ObjectIdentity('1.3.6.1.6.3.1.1.5.2')
                ).addVarBinds(
                    ('1.3.6.1.6.3.1.1.4.3.0', '1.3.6.1.4.1.20408.4.1.1.2'),
                    ('1.3.6.1.2.1.1.1.0', OctetString('my system'))
                )
            )
        )

        if errorIndication:
            print(errorIndication)
        elif errorStatus:
            print('%s: at %s' % (errorStatus.prettyPrint(),
                                 errorIndex and varBinds[int(errorIndex) - 1][0] or '?'))
        else:
            for varBind in varBinds:
                print(' = '.join([x.prettyPrint() for x in varBind]))

        snmpEngine.transportDispatcher.closeDispatcher()

    trollius.get_event_loop().run_until_complete(run())

More examples on Notification Originator API usage follow.

- Common notifications
  - SNMPv1 TRAP with defaults

More sophisticated or less popular SNMP operations can still be performed with PySNMP through its Native API to Standard SNMP Applications.