[AGENT++] How can I use ACE in SNMP++ and Agent++?

[Martin Janzen]

Xiao Wu wrote:
> Hi all,
> My task is to write a remote administration interface and I decided to
> use SNMP.
> For some reason, this task must be ACE-based(adaptive communication
> environment) and I also want to use Agent++, so how can I embed ACE
> network API into Agent++? I means how can I get rid of socket function
> calling in agent++ and replace them with ACE but keep down the other
> parts in Agent++?

We're using ACE as the framework for a process which, among other 
things, acts as an SNMP agent using the Agent++ code.  I would suggest 
that you don't mess around with the Agent++ code at all, but instead use 
the ACE facilities to do a select() for you and to give you a callback 
whenever there is input for the SNMP agent -- something like this:

class MyAgent : public ACE_Event_Handler
{
     MyAgent()
     {
         // Create or find your ACE Reactor.
         mReactor = ... ;

         // Create Agent++ objects as usual.
         mSession = new Agentpp::Snmpx(...);
         mMIB = new Agentpp::Mib(...);
         mRequestList = new Agentpp::RequestList();
         mMIB->set_request_list(mRequestList);
         mRequestList->set_snmp(mSession);

         // Tell ACE to call us back when an SNMP request is received.
         mReactor->register_handler(mSession->get_session_fds(), this,
             ACE_Event_Handler::READ_MASK);
     }

     ~MyAgent()
     {
         // No more callbacks.
         mReactor->deregister_handler(mSession->get_session_fds());

         // Destroy everything else.
         ...
     }

     int handle_input(ACE_HANDLE fd)
     {
         Agentpp::Request* req = mRequestList->receive(0);
	mMIB->process_request(req);
         return CONTINUE;  // Stay registered for more input.
     }
};


Well, that's a bit simplified, but you should get the idea.

(If the request type is an SNMP Set, for instance, you probably want to 
call mMIB->save_all() to save the states of any persistent managed 
objects, maybe after a timeout in case you get lots of Set requests in a 
row.  Also, you should call mMIB->cleanup() periodically, to clean up 
notReady table rows.  But that doesn't have anything to do with ACE...)

Hope that helps!

-- 
Martin Janzen
janzen at pixelmetrix dot com