"""
Send packets from specific local interface
++++++++++++++++++++++++++++++++++++++++++

Send a series of SNMP GETNEXT requests with the following options:

* with SNMPv2c, community 'public'
* over IPv4/UDP
* to an Agent at 104.236.166.95:161
* sending packets from primary local interface 0.0.0.0, local port 61024
* for two OIDs in tuple form
* stop on end-of-mib condition for both OIDs

This script performs similar to the following Net-SNMP command:

| $ snmpwalk -v2c -c public -ObentU 104.236.166.95 1.3.6.1.2.1.1 1.3.6.1.4.1.1

"""#
from pysnmp.entity import engine, config
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.entity.rfc3413 import cmdgen

# Create SNMP engine instance
snmpEngine = engine.SnmpEngine()

#
# SNMPv1/2c setup (if you use SNMPv1 or v2c)
#

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

# Specify security settings per SecurityName (SNMPv1 - 0, SNMPv2c - 1)
config.addTargetParams(snmpEngine, 'my-creds', 'my-area', 'noAuthNoPriv', 0)

#
# Setup transport endpoint and bind it with security settings yielding
# a target name
#

# UDP/IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpSocketTransport().openClientMode(('0.0.0.0', 61024))
)
config.addTargetAddr(
    snmpEngine, 'my-router',
    udp.domainName, ('104.236.166.95', 161),
    'my-creds'
)


# Error/response receiver
# noinspection PyUnusedLocal,PyUnusedLocal,PyUnusedLocal
def cbFun(snmpEngine, sendRequestHandle, errorIndication,
          errorStatus, errorIndex, varBindTable, cbCtx):
    if errorIndication:
        print(errorIndication)
        return
    if errorStatus:
        print('%s at %s' % (errorStatus.prettyPrint(),
                            errorIndex and varBindTable[-1][int(errorIndex) - 1][0] or '?'))
        return  # stop on error
    for varBindRow in varBindTable:
        for oid, val in varBindRow:
            print('%s = %s' % (oid.prettyPrint(), val.prettyPrint()))
    return 1  # signal dispatcher to continue


# Prepare initial request to be sent
cmdgen.NextCommandGenerator().sendVarBinds(
    snmpEngine,
    'my-router',
    None, '',  # contextEngineId, contextName
    [((1, 3, 6, 1, 2, 1, 1), None),
     ((1, 3, 6, 1, 2, 1, 11), None)],
    cbFun
)

# Run I/O dispatcher which would send pending queries and process responses
snmpEngine.transportDispatcher.runDispatcher()
