Asynchronous SNMP engine
The pysnmp.asynsnmp module defines the async_session class,
which implements SNMP engine within Sam Rushing's asyncore framework. For
more information on the asynchronous, non-blocking I/O techniques and their
Python implementation, please, see Sam's
tutorial.
The most important feature of asynchronous SNMP engine is that it can
send and receive a number of SNMP requests virtually simultaneously, as
well as handling some other, file descriptor based input/output activity at
the same time. See examples/async_snmpget.py tool (supplied with PySNMP
distribution) as an example of binding SNMP manager into Telnet server.
The async_session class subclasses the
session class (which implements basic SNMP engine)
so public attributes of session class become available to user
of async_session class.
The pysnmp.async_session module itself defines the following items:
-
async_session(agent, community, callback_fun[, callback_data])
-
Returns a new instance of the async_session class,
representing asynchronous SNMP engine suitable for sending SNMP messages
to and receiving from SNMP process running on host agent,
with SNMP community name.
The callback_fun and optional callback_data
arguments are references to user function and execution context respectively.
The callback_fun function will be invoked by SNMP engine upon
SNMP response arrival.
The following arguments will be passed along with the
callback_fun(callback_data, encoded_oids, encoded_vals) function upon invocation:
-
callback_data holds a reference to user execution context
as specified on class instance creation
-
encoded_oids a list of BER encoded SNMP Object IDs received
with SNMP response
-
encoded_vals a list of BER encoded values associated with
SNMP Object IDs encoded_oids. Object IDs and their respective
values are matched by their positions in the lists.
Unsuccessful requests are indicated by empty entries in the
encoded_oids and encoded_vals lists
returned.
Instances of the async_session class can be reused for
performing a number of SNMP requests to the same SNMP party.
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