sthomen / snmphelper

Helper class for SNMP4J

SnmpHelper

Version 1.4

This is a small class that makes working with SNMP4J much simpler for non-complicated queries.

It completely encapsulates the many SNMP4J classes and provides chainable methods for setting up get, set and walk queries to SNMPv1, v2c and v3 Agents.

This version of SnmpHelper is built on SNMP4J 2.5 (2.5.6 specifically).

Building

There's a small build.bat script for windows hosts. Make sure that you have the JDK installed and then just drop the snmp4j jar in the base directory of the source and run the script.

If your environment is correctly configured (i.e it has JAVA_HOME properly set), everything should work and you'll end up with a SnmpHelper.jar. It contains a manifest with a dependency for the version of snmp4j jar you build it with.

Usage

Usage of the class is fairly straightforward, the class defaults to SNMPv2c with the community name public, so if that's your setup the great! All you have to do is...

SnmpHelper helper = new SnmpHelper();
helper.setAddress("udp:192.168.0.1/161");

To set it up and you can then run...

String uptime=helper.get("1.3.6.1.2.1.1.1.0");

...to get the uptime of the server on 192.168.0.1. Note that this is a very simple library and thus does NOT do any MIB loading. SNMP4J does not seem to include these in the jar and thus you can't--for instance --say SNMPv2-MIB::sysDescr.0.

There are two more "end point" methods in the SnmpHelper class, those are set and walk. As you might imagine, they let you set a single OID and walk a tree based at a given OID.

The syntax is deliberately simple, all you need to do is feed it a base OID (as a string) and for the set method, an SNMP type (since that is required when setting values) and the value as a string or integer.

// update SNMPv2-MIB::sysLocation.0
helper.set("1.3.6.1.2.1.1.6.0", "string", "Server room 2, rack A1");

For numeric types like INTEGER or GAUGE32, you can use a string or an int as the value argument.

Walk is a litte more complicated, you still only give it an OID where to start the walk, but it returns a SnmpHelperTree object instead, from which you can retreive a Map with a string key and a string value (all return values are strings, even those of gauges or integers)

To walk a tree and get the values, do:

SnmpHelperTree tree = helper.walk("1.3.6");
Map<String,String> contents = tree.getContents();

So what if I don't want to use the defaults?

That's also possible, for v1 and v2c, there isn't much to do, just use helper.setCommunity("private") to change the community to use to private and to use SNMPv1, just say helper.setVersion("1").

But what about SNMPv3?

SNMPv3 is a bit more complicated, for that you'll need to know what Authentication mechanism and Privacy mechanism your server uses as well as the username and all the passwords used. The defaults for v3 are no authentication, no privacy and no passwords, so in order to set up (for instance) password authentication using the SHA AuthType, and the user _xkcd _with the password correcthorsebatterystaple but no privacy (encryption) you would do:

SnmpHelper helper = new SnmpHelper();
helper.setAuthHash("sha")
	.setAuthPassword("correcthorsebatterystaple")
	.setUsername("xkcd")
	.setVersion("3")
	.setAddress("udp:192.168.0.1/161");

String location = helper.get("1.3.6.1.2.1.1.6.0");

As you can see, all but the methods that return values are chainable to make it easier to use.

SnmpHelper automatically sets the security level depending on what values you've filled in, if no Privacy is set, then it will not attempt to use it.

What if there's no values or something goes wrong?

This is curretly the weak point of this library, I haven't really built any error checking into it.

As for now, any missing values when doing a get will return null, set does not do error checking. Walk might even break if no values are returned, so be careful.

This may be addressed in future versions.