高分请教大家一个snmp4j相关问题

我想使用snmp4j与设备通信,是不是首先要知道snmp的版本,和oid,oid怎么获取
           String ip = "192.168.100.1";
           Address targetAddress = GenericAddress.parse("udp:" + ip + "/161");
            log.debug("ip"+ip);
            TransportMapping transport;
            transport = new DefaultUdpTransportMapping();
            Snmp snmp = new Snmp(transport);
            transport.listen();
            CommunityTarget target = new CommunityTarget();
            target.setCommunity(new OctetString("public"));
            target.setAddress(targetAddress);
            target.setRetries(2);
            target.setTimeout(1000);
            target.setVersion(SnmpConstants.version1);
            // creating PDU
            PDU pdu = new PDU();            String oidPrefix = "1.3.6.1.2.1.1.1";
            pdu.add(new VariableBinding(new OID(oidPrefix )));
            pdu.setType(PDU.GET);            ResponseEvent event = snmp.send(pdu, target);
            PDU resposePDU = event.getResponse();
     
            Vector result = resposePDU.getVariableBindings();
            VariableBinding vb = (VariableBinding) result.get(0);
            String sID = vb.getVariable().toString();
            log.debug("sID"+sID);这样取对不对,为什么每次result 中的值都是空的,有做过的兄弟给个例子吧,多谢了