Java Dynamic Management Kit 4.2 Tutorial

The Master Agent

The master agent needs to instantiate one SNMP proxy object for each sub-agent containing MIBs that it wishes to serve. The remote MIBs can be on any number of sub-agents, and the master agent can have several proxy objects. Sub-agents themselves may contain proxies: it is up to the designer to define the complexity of the agent hierarchy.

The master agent may also contain a mix of proxies and MBeans for other MIBs. In the proxy example, the master agent exposes the DEMO MIB through local MBeans and a subset of the RFC1213 MIB through a proxy.

Example 19-1 The Master Agent of the Example

MBeanServerImpl server;
ObjectName snmpObjName;
ObjectName localMibObjName;
ObjectName remoteMibObjName;
int htmlPort = 8082;
int snmpPort = 8085;

// read sub-agent connection info from the command line
String host = argv[0];
String port = argv[1];

try {
    server = MBeanServerFactory.createMBeanServer();
    String domain = server.getDefaultDomain();

    // Create and start the HTML adaptor.
    [...]
      
    // Create and start the SNMP adaptor.
    [...]
  
    // Create, initialize, and bind the local MIB Demo.
    //
    localMibObjName = new ObjectName("snmp:class=DEMO_MIB");
    server.registerMBean(localMib, localMibObjName);
    localMib.setSnmpAdaptorName(snmpObjName);
  
    // Create and initialize the SNMP proxy.
    //
    remoteMibObjName = new ObjectName("snmp:class=proxy");
    SnmpMibAgentImpl remoteMib = new SnmpMibAgentImpl();
    server.registerMBean(remoteMib, remoteMibObjName);
    remoteMib.initializeProxy(host, Integer.parseInt(port), "1.3.6.1.2.1");

    // Bind the MIB proxy to the SNMP adaptor
    //
    ((SnmpMibAgent)remoteMib).setSnmpAdaptorName(snmpObjName);
  
} 
catch (Exception e) {
    e.printStackTrace();
    java.lang.System.exit(1);
}

We register the proxy object as for any other MBean and then initialize it. We call the initialize method of the proxy, giving the host and port of the sub-agent it must communicate with, and the root OID of the MIB or subset that it represents.

A single proxy object can serve several MIBs on a sub-agent, and in this case, the OID is the common prefix of all objects. However, the OIDs of all proxies and MIBs in an agent must be distinct, none may be a substring of another (see "Binding the MIB MBeans"). Finally, we bind the proxy to the SNMP adaptor just as we would a MIB MBean.