The DPI GET packet holds one or more varBinds that the subagent has taken responsibility for.

If the subagent encounters an error while processing the request, it creates a DPI RESPONSE packet with an appropriate error indication in the error_code field and sets the error_index to the position of the varBind at which the error occurs. The first varBind is index 1, the second varBind is index 2, and so on. No name, type, length, or value information needs to be provided in the packet because, by definition, the varBind information is the same as in the request to which this is a response and the agent still has that information.

If there are no errors, the subagent creates a DPI RESPONSE packet in which the error_code is set to SNMP_ERROR_noError (0) and error_index is set to 0. The packet must also include the name, type, length, and value of each varBind requested.

When you get a request for a nonexisting object or a nonexisting instance of an object, you must return a NULL value with a type of SNMP_TYPE_noSuchObject or SNMP_TYPE_noSuchInstance respectively. These two values are not considered errors, so the error_code and error_index values should be 0.

The DPI RESPONSE packet is then sent back to the agent.