On 12/11/2013 22:37, Quoth shada:

can i make two io_service::strand instance whith same one io_service instance?

Yes, that's a common usage case. Just bear in mind that the strand only guarantees exclusive execution for handlers executed via the same instance, so (if you have multiple threads running the io_service) you could have one handler from each strand executing simultaneously; just not two handlers from the same strand. Also, for future reference, this sort of query is better directed to the boost-user list rather than here.