I'm having difficulty with latency when running an async asio udp socket. I don't have the same problems with an identical application that uses synchronous udp. I'm communicating with a physical device which permits a maximum 5ms latency for each UDP packet, and I'm currently getting a latency of 8ms with a std dev of 0.065ms which is surprisingly precise.

I'm on Mac OS X 10.10.4 with Xcode 6.3.2 (6D2105).

Here are some of the key details about this problem:

Sync UDP test program

works, staying under 5ms latency 100% of the time for over an hour
Code

main file KukaFRIClientDataTest.cpp
UDP socket communication class KukaFriClientData.hpp

Key lines

calls socket.receive_from() then socket.send() at the lowest level.
receive_from call
send call

Async UDP test program

buggy, 8ms w/ 0.065 ms std dev, continuously high latency
Code

main file KukaFRITest.cpp
High level wrapper class KukaFRIThreadSeparator.hpp
Low level wrapper class KukaFRI.hpp.

Key lines

calls socket_.async_receive_from() then that handler calls socket_.async_send_to(), which calls the final callback with the results.
async_receive_from call
async_send_to_call

Does anyone have insight into why this latency issue may be occurring in the Async UDP version? Thanks.

Cheers!

Andrew Hundt