SNMP4J is one of the most popular Java library for SNMP (Simple Network Management Protocol) operartions. Its quite powerful and easy to use. But it seriously lacks a good documentation. In my project at work, which is a concurrent environment, I faced a funny problem.
I was using a simple snmp trap listener code as shared in the java docs and in numerous amount of blogs. But, the listener use to stop working after a while. Little more debugging and I figured out that it use to stop working only after somewhere else in the code someone has used the same library for SNMP get operation.
Then, i went ahead googling to see if anyone else has ever faced a similar problem. But in vain! Checked the bug list on SNMP4J to see if any such similar issue exists. No luck again! Then I decided to understant the scenario properly and started reading the SNMP4J java source code and Bazinga!!
The very basic source code share with the documentation gives us a wrong implementation of the trap listener. The SecurityModels class is a static class. And when we add user to the ids given, it overrides the previous user. So the right way to add USM user is:
USM usm = (USM) SecurityModels.getInstance().getSecurityModel(
new Integer32(USM.SECURITY_MODEL_USM));
if (usm == null) {
usm = new USM(SecurityProtocols.getInstance(), new OctetString(
MPv3.createLocalEngineID()), 0);
SecurityModels.getInstance().addSecurityModel(usm);
}
UsmUser myuser = new UsmUser(new OctetString(USERNAME), AuthMD5.ID,
new OctetString(PASSWORD), null, null);
usm.addUser(new OctetString(USERNAME), myuser);
With this we way don't override the USMUser and our code works fine. Woila! This discovery took a huge amount of my time. Hope it helps someone.
I was using a simple snmp trap listener code as shared in the java docs and in numerous amount of blogs. But, the listener use to stop working after a while. Little more debugging and I figured out that it use to stop working only after somewhere else in the code someone has used the same library for SNMP get operation.
Then, i went ahead googling to see if anyone else has ever faced a similar problem. But in vain! Checked the bug list on SNMP4J to see if any such similar issue exists. No luck again! Then I decided to understant the scenario properly and started reading the SNMP4J java source code and Bazinga!!
The very basic source code share with the documentation gives us a wrong implementation of the trap listener. The SecurityModels class is a static class. And when we add user to the ids given, it overrides the previous user. So the right way to add USM user is:
USM usm = (USM) SecurityModels.getInstance().getSecurityModel(
new Integer32(USM.SECURITY_MODEL_USM));
if (usm == null) {
usm = new USM(SecurityProtocols.getInstance(), new OctetString(
MPv3.createLocalEngineID()), 0);
SecurityModels.getInstance().addSecurityModel(usm);
}
UsmUser myuser = new UsmUser(new OctetString(USERNAME), AuthMD5.ID,
new OctetString(PASSWORD), null, null);
usm.addUser(new OctetString(USERNAME), myuser);
With this we way don't override the USMUser and our code works fine. Woila! This discovery took a huge amount of my time. Hope it helps someone.