Receive can miss multiple PDUs in buffer

[weili-jiang]

Thanks for continuing the work from the original. I've reviewed the delta and it looks like this fork is still susceptible to the issue fixed by this PR: hosthvo/pyagentx#18

The code looks similar enough that I think the proposed patch would still largely apply. What do yo think?

[rprinz08]

You are right. It might be possible to miss a PDU. Should be fixed with commit 9e9f5fa