Working with Protocol Data Units

The Simple Network Management Protocol sends operation requests and responses as SNMP messages. An SNMP message is an SNMP protocol data unit (PDU) plus additional message header elements defined by the relevant RFC. A PDU includes a variable binding list.

The structure of a PDU is restricted to the Microsoft WinSNMP implementation. A WinSNMP application can access a PDU with a handle of the type HSNMP_PDU. The WinSNMP application must create a PDU before it calls the SnmpSendMsg function or the SnmpEncodeMsg function.

The application can extract and update the data elements of a PDU, and release resources allocated for PDUs. To perform these operations, the application uses the WinSNMP PDU functions. For additional information about working with PDUs in the WinSNMP programming environment, see the following topics:

• Creating a PDU
• Updating a PDU
• Duplicating a PDU
• Validating a PDU
• Matching Response and Request PDUs

For more information, see Working with Variable Binding Lists and Resource Handle Objects.