decodesnmpmessage.java

DecodeSNMPMessage java编程解码

//DecodeSNMPMessage.java
//*"*************************************************************************
//          此类实现了对5类不同的SNMP消息的解封装,它的功能有:               *
//          1.解封装GetRequestPDU                                           *
//          2.解封装GetNextRequestPDU                                       *
//          3.解封装SetRequestPDU                                           *
//          4.解封装GetResponsePDU                                          *
//          5.解封装TrapPDU                                                 *
//..........................................................................*
//          Creted by:  ZhuSiFeng(朱思峰)                                   *
//          Email him:  [e-mail]                          *
//*"***************************************************"*********************  

import java.io.*; 
import java.net.*; 
//import java.lang.*;



public class DecodeSNMPMessage
{
 
  //*"*****************************定义公用方法,供其它方法调用*************"*********************  
  //将String类型的result打印出来
  void PrintBytes(String result)
	  {
         byte temp1[] = result.getBytes();
         int  chInt;
         for(int i = 0;i<temp1.length;i++)
		  {
               chInt = temp1[i];
              if(temp1[i]<0)
			   {
                chInt += 256;
                }
            int temp3 = chInt/16;
            int temp4 = chInt-temp3*16;
            char  ch,ch1;
            if( temp3 < 10 )
				ch =(char)(temp3 + 48);
            else
				ch =(char) (temp3 + 55);
            if( temp4 < 10 )
				ch1 = (char)(temp4 + 48);
            else
				ch1 = (char)(temp4 + 55);
            System.out.print(ch);
            System.out.print(ch1);
            System.out.print(" ");
        }
    }

  //将byte类型数转换为int类型数，认为byte是无符号数
   int  ByteToInt(byte temp1)
	  {
            int  chInt = temp1;
            if( temp1 < 0 )
			 {
                chInt += 256;
             }
            return chInt;
      }
  
  //将byte数组temp1中所有元素打印出来（以16进制的形式）
  void PrintBytes(byte temp1[])
	  {
        int  chInt;
        for(int i = 0;i<temp1.length;i++)
		  { chInt = temp1[i];
            if(temp1[i]<0)
				{chInt += 256;}            
            int temp3 = chInt/16;
            int temp4 = chInt-temp3*16;
            char  ch,ch1;
            if( temp3 < 10 )
				ch =(char)(temp3 + 48);
            else
				ch =(char) (temp3 + 55);
            if( temp4 < 10 )
				ch1 = (char)(temp4 + 48);
            else 
				ch1 = (char)(temp4 + 55);
            System.out.print(ch);
            System.out.print(ch1);
            System.out.print(" ");
         }
    }
    
  //将byte数组temp1中的前nLength长度的元素打印出来（以16进制的形式）
  void PrintBytes(byte temp1[],int nLength)
	  {
        int  chInt;
        for(int i = 0;i<nLength;i++)
		 {
            chInt = temp1[i];
            if(temp1[i]<0)
				{ chInt += 256;}
            int temp3 = chInt/16;
            int temp4 = chInt-temp3*16;
            char  ch,ch1;
            if( temp3 < 10 ) 
				ch =(char)(temp3 + 48);
            else 
				ch =(char) (temp3 + 55);
            if( temp4 < 10 ) 
				ch1 = (char)(temp4 + 48);
            else
				ch1 = (char)(temp4 + 55);
            System.out.print(ch);
            System.out.print(ch1);
            System.out.print(" ");
         }
     }
    
  //将temp0字符串转换为相应的数  
  int   StringToInt(String temp0)
	  {
        if (temp0.length() == 0)
			return 0;
        int  retValue = 0;
        for (int i = 0; i < temp0.length();i++)
			{
             char  temp1 = temp0.charAt(i);
             retValue =retValue*10+(int)temp1 - 0x30;
            }   
        return retValue; 
      }  



//*"*****************************定义主要方法*************"*********************  
//该方法的功能: 1. 解码并打印解码结果 2.通过数组返回解码结果
 public void DecodePDU(byte message[],byte outcommunity[],byte outrequestID[],byte outvarBind[])
 {   
	 //说明: 该函数完成下面的任务:
	 //0.解析出版本信息;
	 //1.解析出团体字符串commnunitty信息到community[]中;
	 //2.解析出消息的PDU-TYPE编码
	 //3.解析出request-id信息到requestID[]中;
	 //4.解析出error-status信息;
	 //5.解析出error-index信息;
	 //6.解析出Variable-bindings信息到varBind[]中;
	 int   messageLength;//消息体长度  
	 int   commLength; //团体字符串长度  
	 int   requestIDLength;//Request_ID长度 
	 int   varBindLength; //整个varBindList的长度，从sequence of 开始，初值为2 
	 byte  version;
	 byte  community[]  = new byte[10];//团体字符串临时存储
	 byte  PDu_type;
	 byte  error_status;
	 byte  error_index;
	 byte  requestID[]  = new byte[10]; //RequestID临时存储
	 byte  varBind[]    = new byte[1024]; //绑定变量表临时存储
         int i; 
	 int index=1;//用于指示数组message中的某个位置

     //------------------------------------------------------------------------------------
	 //解码过程
	 messageLength = ByteToInt(message[index]);
	 index= index+3;//index=4

	 //0.解析出版本信息到version[]中;	 
	  version= message[index];
	  index=index+2;

	 //1.解析出团体字符串commnunitty信息到ocommunity[]中;
	 commLength= ByteToInt(message[index]);
	 index++;
	 for(i=0;i<=commLength-1;i++)
		 community[i] = message[i+index];
	 index= index+commLength;

	 //2.解析出GetRequest的PDU-TYPE编码	 
	 PDu_type = message[index];
	 index = index+3;

	 //3.解析出request-id信息到requestID[]中;
	 requestIDLength= ByteToInt(message[index]);
	 index++;
	 for(i=0;i<=requestIDLength-1;i++)
		 requestID[i] = message[index +i];
	 index = index+ requestIDLength +2;

	 //4.解析出error-status信息;
	 error_status = message[index];
	 index = index+3;

	 //5.解析出error-index信息中;
	 error_index = message[index];
	 index= index +1;

	 //6.解析出Variable-bindings信息到varBind[]中;
	 varBindLength = ByteToInt(message[index+1]);
	 for(i=0;i<=varBindLength-1+2;i++)
		 varBind[i] = message[index+i];


      //------------------------------------------------------------------------------------
	 //打印解码结果
     System.out.println("\n		解码结果如下(Decode result as follow): ");
	 System.out.print("		消息体长度(messageLength): ");
	 System.out.println(messageLength);
  	 System.out.print("		SNMP版本信息(SNMP Version): ");
	 System.out.println(ByteToInt(version));
	 System.out.print("		团体字符串(Community): ");
	 PrintBytes(community);
	 System.out.print("\n		PDU类型(PDU_TYPE): ");
	 byte tmp[]= new byte[1];	 
	 tmp[0]=PDu_type;
	 PrintBytes(tmp);
	 System.out.print("\n		请求编号(RequestID): ");
	 PrintBytes(requestID);
	 System.out.print("\n		错误类型(error_status): ");
	 tmp[0]=error_status;
	 PrintBytes(tmp);
	 System.out.print("\n		错误位置(error_index): ");
	 tmp[0]=error_index;
	 PrintBytes(tmp);
	 System.out.print("\n		变量绑定(Variable_bindings): ");
	 PrintBytes(varBind);
	 //------------------------------------------------------------------------------------
	//通过数组返回解码结果
	for(i=0;i<= commLength-1;i++)
		outcommunity[i]=community[i];
	for(i=0;i<=requestIDLength-1; i++)
		outrequestID[i] =  requestID[i];
	for(i=0;i<=varBindLength-1;i++)
		outvarBind[i] = varBind[i];
	return;


  }//end_of_DecodePDU()
 
}//end_of_class