SNMP++的深入学习(二)

二、必须经过的阶段Vb类、Pdu类
使用Vb类，主要目的是在处理返回的SNMP应答包时，获得返回的SNMP变量值，有时也需要获得返回的SNMP变量OID。
源代码如下：
#include "snmp_pp.h"
#include "oid.h"
#include "vb.h"
#include
void main()
{
   // -------[Ways to construct Vb objects ]-------
   // construct a single Vb object 定义一个vb1
   Vb vb1;
 
   // construct a Vb object with an Oid object
   // this sets the Oid portion of the Vb
   Oid d1("1.3.6.1.4.12"); //定义了一个Oid d1，值为1.3.6.1.4.12
   Vb vb2(d1);//用d1来为vb2赋值
   cout<<"vb2's oid is "< 
   // construct a Vb object with a dotted string 用一个点分制字符串来定义vb3的oid值
   Vb vb3( (Oid) "1.2.3.4.5.6");
   cout<<"vb3's oid is "< 
   // construct an array of ten Vbs
   Vb vbs[10];
 
   //------[Ways to set and get the Oid portion of Vb objects ]
 
   // set and get the Oid portion portion的意思是part piece
  Oid d2((Oid)"1.2.3.4.5.6");
   vb1.set_oid(d2); //用d2的值来定义vb1的oid值，由于现在d2值为1.2.3.4.5.6，所以vb1的oid值也为1.2.3.4.5.6
   cout<<"vb1's oid is "<   Oid d3;
   vb1.get_oid(d3); //d3取vb1的oid,由于vb1的oid值是用d2的值来定义的，所以d3的值也为1.2.3.4.5.6
   cout<<"d3's oid is "<   if (d2==d3) cout << "They better be equal!!/n";
 
   Vb ten_vbs[10];
   int z;
   for (z=0;z<10;z++)
   ten_vbs[0].set_oid((Oid)"1.2.3.4.5"); //先对ten_vbs[0]的值作了一个定义
 
   //-------[ ways to set and get values ]
 
   // set & get ints
   int x,y;
   x=5;
  vb1.set_value(x); //将vb1的value值设为x的值，即为5
  cout<<"vb1'value is "<   vb1.get_value(y);//将vb1的value值设给y
   cout<<"y is "<   if ( x == y) cout << "x equals y/n";
   // set and get long ints
   long int a,b;
   a=100;
 cout<<"a is "<//-------[ ways to set and get values ]
   if ( a == b)  cout << "a equals b/n" ;
    else cout<<"a is not equals b/n";
   // set & get unsigned long ints
 unsigned long int c,d;
 c = 1000;
 
  vbs[0].set_value( c);  //将vbs[0]的value值设为1000
  vbs[0].get_value( d);  //用vbs[0]值设y的值
   if ( c == d) cout << "c equals d/n";
 
   // set a 64 bit counter
   Counter64 c64(1000,1001);
  vbs[1].set_value( c64);
 
   // get and set an oid as a value
   Oid o1, o2;  //定义两个Oid o1 o2
   o1 = "1.2.3.4.5.6";
   vbs[2].set_value( o1);  //将vbs[2]的value值设为o1即1.2.3.4.5.6
   vbs[2].get_value( o2);  //将o2的值设为1.2.3.4.5.6
   if ( o1 == o2) cout << "o1 equals o2/n";
 
   // set and get an octet string
   unsigned char data[4],outdata[4];
   unsigned long len,outlen;
   len =4; data[0] = 10; data[1] = 12; data[2] = 12; data[3] = 13;
   OctetStr octetstr(data,len);
   vbs[3].set_value( octetstr);
   vbs[3].get_value( octetstr);
 
   // get & set a string
   char beer[80];  //定义了一个字符串beer
   char good_beer[80]; //定义了一个字符串good_beer
   strcpy( beer,"Sierra Nevada Pale Ale");
   cout<<"beer is "<  vbs[4].set_value( beer); //将beer的值设置给vbs[4]的value
   vbs[4].get_value( good_beer); //又将good_beer的值设置为beer的值
   printf("Good Beer = %s/n",good_beer);
   // get and set an ip an address
  IpAddress ipaddress1, ipaddress2;
   ipaddress1 = "10.4.8.5";
   vbs[5].set_value( ipaddress1);
   vbs[5].get_value( ipaddress2);
   cout << "ipaddress2 is "< 
} // end vb example
运行结果如图7所示

 

图7
Pdu class作为Snmp class的接口，处理SNMP请求
源代码如下：
#include "snmp_pp.h"
#include
#define SYSDECR "1.3.6.1.2.1.1.1.0"
// example of how to load a Pdu object
void main()
{
  Pdu pdu;                                 // create a Pdu object
  //创建了一个pdu
   Vb vb;                                          // create a Vb object
   //创建了一个vb对象
  vb.set_oid( SYSDECR);             // set the oid portion of the Vb to System Descriptor
  //将vb的oid值定义为SYSDECR，也即为1.3.6.1.2.1.1.1.0
  cout<<"vb's oid is "<   pdu += vb;                                  // loads the Vb to the Pdu
   //将vb的值赋给pdu
 //  cout<   pdu.get_vb(vb,0);
   cout< 
   Pdu my_pdu;                         // create another Pdu object
  Vb vbs[5];                                  // create 5 vbs
  pdu.set_vblist( vbs,5);                // load all 5 to the pdu
}
从阻塞或异步请求中得到请求的Pdu后，都需要将Vb卸载下来才能把SMI values取出
源程序如下：
// example of how to unload a Pdu
#include "snmp_pp.h"
#include
#define SYSDECR "1.3.6.1.2.1.1.1.0"
void main()
{
 Snmp::socket_startup();
   int status=0;
   Pdu pdu;                                 // create a Pdu object
  Vb vb;                                          // create a Vb object
  vb.set_oid( SYSDECR);             // set the oid portion of the Vb to System Descriptor
  pdu += vb;                                  // loads the Vb to the Pdu
   char message[100];                 // for the system descriptor printable octet
 
   Snmp snmp( status);
   if ( status != SNMP_CLASS_SUCCESS) {
      cout << "SNMP++ error = "<< snmp.error_msg( status) ;
      return;
   }
 
   pdu.get_vb( vb,0);                        // unload the vb
   vb.get_value( message);         // pull the message out of the vb
   cout << "messages is "< 
}