关于snmp4j的问题，求助！！！！！

一小段用SNMP4J读取OID的代码，请大家给看看，为啥运行的时候返回的是两个null啊？protocol.send()这个函数没有把值传给response？是不是还要有agent端之类的，请明白人给小妹分析一下吧，谢谢了 import   org.snmp4j.*; 
import   org.snmp4j.transport.*; 
import   java.io.*; 
import   org.snmp4j.smi.*; 
import   org.snmp4j.mp.*; 
import   org.snmp4j.event.*; class   snmptest{   
                public   static   void   main(String[]   args){ 
                
                try{ 
                TransportMapping   transport1   ; 
                transport1   =   new   DefaultUdpTransportMapping(); 
                  Snmp   protocol   =   new   Snmp(transport1); 
                  transport1.listen(); 
                  CommunityTarget   myTarget   =   new   CommunityTarget(); 
                  Address   deviceAdd;//org.snmp4j.smi.*; 
                deviceAdd   =   GenericAddress.parse("udp:127.0.0.1/161"); 
                myTarget.setAddress(deviceAdd); 
                myTarget.setCommunity(new   OctetString("public")); 
                myTarget.setRetries(0); 
                myTarget.setTimeout(5*60);         
                myTarget.setVersion(SnmpConstants.version2c);//org.snmp4j.mp.*; 
                PDU   pdu   =   new   PDU(); 
                VariableBinding   var   =   new   VariableBinding(new   OID("1.3.6.1.4.1.9.2.1.8.0")); 
                pdu.add(var); 
                pdu.setType(PDU.GET); 
                ResponseEvent   response   =   protocol.send(pdu,   myTarget); 
                System.out.println(response.getResponse()); 
                System.out.println(response.getPeerAddress()); 
            }catch(IOException   e){ 
                            e.printStackTrace(); 
                            System.out.println(e.getMessage());                             return; 
            } 
                } 
}