Java Dynamic Management Kit 4.0 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 9-1 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 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 root 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.