如何用snmp4j实现对mib信息的收发的例子，大家给看看哪里出了问题
package snmp; 

import java.io.IOException; 
import java.net.InetAddress; 

import org.snmp4j.CommunityTarget; 
import org.snmp4j.PDU; 
import org.snmp4j.Snmp; 
import org.snmp4j.event.ResponseEvent; 
import org.snmp4j.mp.SnmpConstants; 
import org.snmp4j.smi.OID; 
import org.snmp4j.smi.OctetString; 
import org.snmp4j.smi.UdpAddress; 
import org.snmp4j.smi.VariableBinding; 
import org.snmp4j.transport.DefaultUdpTransportMapping; 

public class test3{ 

  public static void main(String[] args) 
  { 
  try { 
  Snmp snmp = new Snmp(new DefaultUdpTransportMapping()); 
  CommunityTarget target = new CommunityTarget();//agent对象 
  target.setCommunity(new OctetString("public"));//设置共同体名,没发现设置RWCommnity的方 
  //法,大概只能设一个. 
  target.setVersion(SnmpConstants.version2c);//设置版本 
  target.setAddress(new UdpAddress("127.0.0.1/161"));//设置IP地址和端口号,这里竟然用'/'来分  
  //隔,当初确实没有料到,JDOC的说明等于没有. 
  target.setRetries(1); //设置重试次数 
  target.setTimeout(5000); //设置超时 

  snmp.listen(); //监听 
  PDU request = new PDU(); //new request PDU包 
  //set pud type and set oid 
  request.setType(PDU.GET); //设置PDU类型, 
  request.add(new VariableBinding(new OID(".1.3.6.1.2.1.1.1.0"))); //OID添加 
  // request.add(new VariableBinding(new OID(".1.3.6.1.2.1.1.2.0"))); 
  System.out.println("request UDP:" + request);//请求包内内容输出, 
  PDU response = null;//定义response包 
  ResponseEvent responseEvent = snmp.send(request, target); //发出request PDU 
  //接收response PDU 
  response = responseEvent.getResponse(); 

  //response PDU包解析 
  if(response!=null){ 
  if(response.getErrorIndex()==response.noError&&response.getErrorStatus()==response.noError){ 
  System.out.println("no error."); 
  String pause=responseEvent.getResponse().getVariableBindings().toString(); 
  String getvalue=pause.substring( pause.indexOf("= ")+2,pause.indexOf(']')); 
  String oid=pause.substring(pause.indexOf("VBS[")+2,pause.indexOf("=")-1); 
  System.out.println(oid);