Re: A manager using a single socket and multiple agents?

Actually the snmplibrary already has a way of binding the ports.

In my $HOME/.snmp/snmp.conf I just add this:

[asyncapp]
#doDebugging 1
clientaddr 10.0.0.1:12345
clientaddrUsesPort yes

asyncapp is the name of my program. I have bound outbound connections with
a source port of 12345 on interface 127.0.0.1 (for testing)
10.0.0.1 is the local IP address of the computer that's sending the request.

Wireshark shows this:
User Datagram Protocol, Src Port: 12345, Dst Port: 161







On Thu, 7 Jan 2021 at 15:03, Ed Fair <[email protected]> wrote:

> Craig,
>
> The tutorials don't mention subsessions or traditional vs single session
> use, but the header/c files do (and that's all they do - mention them).
> I'm just curious what these abstractions are for since they seem, on the
> surface, related to my needs.
>
> As an exercise, I've tried but so far been unable to create a
> session/socket which uses a specific port - no errors, but no pdus/packets
> transmitted.  And anyway, I don't care if the port selected is random, my
> goal is to use *the same* port to query multiple agents.  I don't care how
> it's done, as long as the end result is "all outbound UDP use same SRC
> port".
>
>
> On Wed, Jan 6, 2021, 5:28 AM Craig Small <[email protected]> wrote:
>
>> On Wed, 6 Jan 2021 at 10:01, Ed Fair <[email protected]> wrote:
>>
>>> Thanks for the reply.  The Simple_Async_Application in your link uses
>>> one session/socket/SRC port per agent.  I've compiled and run this sample
>>> successfully, but I haven't been able to modify it to use a single
>>> session/socket/SRC port.
>>>
>> It might need to be something more low-level as reusing sockets
>> (therefore the ports) is generally a bad idea.
>>
>> The netsnmp_session has an attribute of local_port. If this is set to
>> zero (the default) then it picks it randomly. I'd try setting that and see
>> what happens. A quick look in the snmplib source code shows it is used for
>> creating the transport.
>>
>> I understand "don't hammer agents" but I don't understand your "one query
>>> per agent" limit - is this a limitation of the API?
>>>
>> Not at all, a lot of agents are terrible and do stupid things like have
>> exclusive locks on important components of the system. I've killed many
>> devices (the remote agents, not my code) by being too enthusiastic about
>> querying them.
>>
>>
>>> I'm new to this API, I might be missing key concepts... but I am
>>> confused by the "traditional vs single" distinction, and I'm curious what
>>> "subsessions" are.
>>>
>> Are either of those mentioned in the tutorial? They could mean multiple
>> things but was trying to find the context of what you are asking here.
>>
>>  - Craig
>>
>

_______________________________________________
Net-snmp-coders mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/net-snmp-coders