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 print开发者_JAVA技巧er, 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?

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

Just have a look to the mib :

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.

It looks like your printer is storing a list of states. You have to get bulk starting from OID .1.3.6.1.2.1.43.18.1.1.8.1.1 and use the last variable binding from the group.