SNMP Library for Ruby

Summary

This library implements SNMP (the Simple Network Management Protocol). It is implemented in pure Ruby, so there are no dependencies on external libraries like net-snmp. You can run this library anywhere that Ruby can run.

See snmplib.rubyforge.org for more info.

Version 0.4.0 of this software supports the following:

  • The GetRequest, GetNextRequest, GetBulkRequest, SetRequest, and Response PDUs

  • All of the ASN.1 data types defined by SNMPv1 and SNMPv2c

  • Trap handling for both v1 and v2 traps

  • Symbolic OID values as parameters to the SNMP.Manager API

  • Includes symbol data files for all current IETF MIBs

See the SNMP.Manager, SNMP.TrapListener, and SNMP.MIB classes and the examples below for more details.

Changes

Changes from version 0.3.0:

  • Added support for loading MIBs and using symbolic OID values. (ie. “ifTable” instead of “1.3.6.1.2.1.2.2”)

  • Enhanced Manager.walk

    * It can now take an OID list as a parameter.  (Thanks to Simon
  Barnes for the suggestion.)
* Takes a block instead of returning a list to allow incremental
  processing of results.

  • Some minor improvements to code structure and error messages.

Changes from version 0.2.0:

  • Added SNMPv1_Trap and SNMPv2_Trap classes

  • Added TrapListener class for receiving v1 and v2 traps

  • Added Manager.walk

  • Fixed a problem with IpAddress encoding

  • Defined IpAddress.== and IpAddress.eql? so that IpAddress objects can be compared by value

Changes from version 0.1.0:

  • Added GetBulkRequest

  • Added open and close methods to the Manager class to ensure that sockets can be properly released.

  • Made SNMP::OctetString and SNMP::Integer behave more like Ruby’s String and Fixnum

  • Fixed a problem with encoding/decoding the object id “0.0”

Installation

The SNMP Library can be downloaded from RubyForge in several different formats.

From the .gem file you can install using RubyGems.

gem install snmp-0.4.0.gem

From the .tgz or .zip file you can install using setup.rb. Uncompress the archive and then run setup.

cd snmp-0.4.0
ruby setup.rb (may require root privilege)

You can also use rpa-base or RubyGems to install the latest version of the SNMP library remotely.

rpa install snmp

or

gem install --remote snmp

Testing

So far, this library has received limited testing:

  • The unit tests have been executed with Ruby 1.8.1 on Mac OS X 10.3 and Windows XP.

  • Basic interoperability testing has been done with the net-snmp tools, but not much beyond that.

I’m very interested in hearing about successes or failures on other platforms.

Send me an email at snmp at halliday.ca.

Examples

Get Request

Retrieve a system description.

require 'snmp'
SNMP::Manager.open(:Host => 'localhost') do |manager|
    response = manager.get(["1.3.6.1.2.1.1.1.0", "1.3.6.1.2.1.1.2.0"])
    response.each_varbind do |vb|
        puts "#{vb.name.to_s}  #{vb.value.to_s}  #{vb.value.asn1_type}"
    end
end

Set Request

Create a varbind for setting the system name.

require 'snmp'
include SNMP
manager = Manager.new(:Host => 'localhost')
varbind = VarBind.new("1.3.6.1.2.1.1.5.0", OctetString.new("My System Name"))
manager.set(varbind)
manager.close

Table Walk

Walk the ifTable.

require 'snmp'
ifTable_columns = ["ifIndex", "ifDescr", "ifInOctets", "ifOutOctets"]
SNMP::Manager.open(:Host => 'localhost') do |manager|
    manager.walk(ifTable_columns) do |row|
        row.each { |vb| print "\t#{vb.value}" }
        puts
    end
end

Get-Next Request

A more difficult way to walk the ifTable.

require 'snmp'
include SNMP
Manager.open(:Host => 'localhost') do |manager|
    ifTable = ObjectId.new("1.3.6.1.2.1.2.2")
    next_oid = ifTable
    while next_oid.subtree_of?(ifTable)
        response = manager.get_next(next_oid)
        varbind = response.varbind_list.first
        next_oid = varbind.name
        puts varbind.to_s
    end
end

Get-Bulk Request

Get interface description and admin status for 10 rows of the ifTable.

require 'snmp'
include SNMP
ifDescr_OID = ObjectId.new("1.3.6.1.2.1.2.2.1.2")
ifAdminStatus_OID = ObjectId.new("1.3.6.1.2.1.2.2.1.7")
MAX_ROWS = 10
Manager.open(:Host => 'localhost') do |manager|
    response = manager.get_bulk(0, MAX_ROWS, [ifDescr_OID, ifAdminStatus_OID])
    list = response.varbind_list
    until list.empty?
        ifDescr = list.shift
        ifAdminStatus = list.shift
        puts "#{ifDescr.value}    #{ifAdminStatus.value}"
    end
end

Trap Handling

Log traps to STDOUT.

require 'snmp'
require 'logger'
log = Logger.new(STDOUT)
m = SNMP::TrapListener.new do |manager|
    manager.on_trap_default do |trap|
        log.info trap.inspect
    end
end
m.join

License

This SNMP Library is Copyright © 2004 by David R. Halliday. It is free software. Redistribution is permitted under the same terms and conditions as the standard Ruby distribution. See the COPYING file in the Ruby distribution for details.