Simple SNMP server in pure Python

It is possible to use snmpserver as pytest plugin. This option requires Python >=3.6.

The fixture snmpserver has the host and port attributes (which can be set via environment variables PYTEST_SNMPSERVER_HOST and PYTEST_SNMPSERVER_PORT), along with the expect_request method:

def test_request_replies_correctly(snmpserver):
    snmpserver.expect_request("1.3.6.1.2.1.2.2.1.2", "some description")
    command = shlex.split(f'{snmpget_command} {snmpserver.host}:{snmpserver.port} IF-MIB::ifDescr')
    p = subprocess.Popen(command, stdout=subprocess.PIPE)
    p.wait()
    assert 'IF-MIB::ifDescr some description' == p.stdout.read().decode('utf-8').strip()

It is also possible to use standalone version of SNMP server, which works as an echo server if no config is passed. This version supports Python 2 and 3.

Standalone usage: snmp-server.py [-h] [-p PORT] [-c CONFIG] [-d] [-v]

SNMP server

optional arguments:
  -h, --help            show this help message and exit
  -p PORT, --port PORT  port (by default 161 - requires root privileges)
  -c CONFIG, --config CONFIG
                        OIDs config file
  -d, --debug           run in debug mode
  -v, --version         show program's version number and exit

Examples:

# ./snmp-server.py -p 12345
SNMP server listening on 0.0.0.0:12345
# ./snmp-server.py
SNMP server listening on 0.0.0.0:161

Without config file SNMP server works as a simple SNMP echo server:

# snmpget -v 2c -c public 0.0.0.0:161 1.2.3.4.5.6.7.8.9.10.11
iso.2.3.4.5.6.7.8.9.10.11 = STRING: "1.2.3.4.5.6.7.8.9.10.11"

It is possible to create a config file with values for specific OIDs.

Config file - is a Python script and must have DATA dictionary with string OID keys and values.

Values can be either ASN.1 types (e.g. integer(...), octet_string(...), etc) or any Python lambda/functions (with single argument - OID string), returning ASN.1 type.

DATA = {
  '1.3.6.1.4.1.1.1.0': integer(12345),
  '1.3.6.1.4.1.1.2.0': bit_string('\x12\x34\x56\x78'),
  '1.3.6.1.4.1.1.3.0': octet_string('test'),
  '1.3.6.1.4.1.1.4.0': null(),
  '1.3.6.1.4.1.1.5.0': object_identifier('1.3.6.7.8.9'),
  # notice the wildcards:
  '1.3.6.1.4.1.1.6.*': lambda oid: octet_string('* {}'.format(oid)),
  '1.3.6.1.4.1.1.?.0': lambda oid: octet_string('? {}'.format(oid)),
  '1.3.6.1.4.1.2.1.0': real(1.2345),
  '1.3.6.1.4.1.3.1.0': double(12345.2345),
}

# ./snmp-server.py -c config.py
SNMP server listening on 0.0.0.0:161

With config file snmpwalk command as well as snmpget can be used:

# snmpwalk -v 2c -c public 0.0.0.0:161 .1.3.6.1.4.1
iso.3.6.1.4.1.1.1.0 = INTEGER: 12345
iso.3.6.1.4.1.1.2.0 = BITS: 12 34 56 78 3 6 10 11 13 17 19 21 22 25 26 27 28
iso.3.6.1.4.1.1.3.0 = STRING: "test"
iso.3.6.1.4.1.1.4.0 = NULL
iso.3.6.1.4.1.1.5.0 = OID: iso.3.6.7.8.9
iso.3.6.1.4.1.1.6.4294967295 = STRING: "* 1.3.6.1.4.1.1.6.4294967295"
iso.3.6.1.4.1.1.9.0 = STRING: "? 1.3.6.1.4.1.1.9.0"
iso.3.6.1.4.1.2.1.0 = Opaque: Float: 1.234500
iso.3.6.1.4.1.3.1.0 = Opaque: Float: 12345.234500
iso.3.6.1.4.1.4.1.0 = No more variables left in this MIB View (It is past the end of the MIB tree)

Also snmpset command can be used:

# snmpset -v2c -c public 0.0.0.0:161 .1.3.6.1.4.1.1.3.0 s "new value"
iso.3.6.1.4.1.1.3.0 = STRING: "new value"
#
# snmpget -v2c -c public 0.0.0.0:161 .1.3.6.1.4.1.1.3.0
iso.3.6.1.4.1.1.3.0 = STRING: "new value"

Released under The MIT License.