snmpsharpnet

Dealing with an incrementing SNMP OID?

I'm trying to use SNMP to get data from a printer. If I turn the printer off and on, the OID that I need to get is .1.3.6.1.2.1.43.18.1.1.8.1.1. Each time the printer has an "event", such as getting paused, running out of paper or having a paper jam, the OIDfor the data I want increments.

For example, I turn the printer on and query .1.3.6.1.2.1.43.18.1.1.8.1.1. and I get "paused" as the value. I unpause the printer and remove all of the paper from the printer, and to get the "add paper" message I have to query .1.3.6.1.2.1.43.18.1.1.8.1.2.

I don't know if this is normal SNMP behavior but I wonder what people suggest I do in these cases to be able to programatically get the printer state?

Solution

  • Yes it's normal you are retreiving rows from an alert table :

    Just have a look to the mib :

    enter image description here

    The corresponding text part of the mib is (from RFC 1759):

    prtAlertTable OBJECT-TYPE
    SYNTAX     SEQUENCE OF PrtAlertEntry
    MAX-ACCESS not-accessible
    STATUS     current
    DESCRIPTION
        ""
    ::= { prtAlert 1 }

prtAlertEntry OBJECT-TYPE
    SYNTAX     PrtAlertEntry
    MAX-ACCESS not-accessible
    STATUS     current
    DESCRIPTION
        "Entries may exist in the table for each device
        index who's device type is `printer'."
    INDEX  { hrDeviceIndex, prtAlertIndex }
    ::= { prtAlertTable 1 }

PrtAlertEntry ::= SEQUENCE {
    prtAlertIndex               Integer32,
    prtAlertSeverityLevel       INTEGER,
    prtAlertTrainingLevel       INTEGER,
    prtAlertGroup               INTEGER,
    prtAlertGroupIndex          Integer32,
    prtAlertLocation            Integer32,
    prtAlertCode                INTEGER,
    prtAlertDescription         OCTET STRING,
    prtAlertTime                TimeTicks
}

    So the way SNMP works is to is to suffix the OID entry of the MIB by the index of the row. You can get the whole table by a Get-Bulk, but I think that the first thing for you is to understand how to retreive an SNMP table.

    In your exact case : 1.3.6.1.2.1.43.18.1.1.8.1.1 you have to read it as :

    1.3.6.1.2.1.43.18.1.1.8 : prtAlertDescription followed by

    1 : the hrDeviceIndex followed by

    1 : the prtAlertIndex which is the row.

    An Advice you can find an assembly called snmpsharpnet which is very helpful to play with SNMP on the top of .NET.