nio multi thread client performance

[A.R.]

I've a java program to manage servers (in fact gauges) by tcp/ip.
There is a thread per connection. I used nio and non-blocking mode
There is requirements that requests (about 50 bytes) should be send to
server i.e. every 20ms - 1s.
I tested performance with one connection and found response time
sometimes fluctuate from from 10ms to 500ms.

Any help welcome (i.e. tcp/ip send and receive buffer size or other
parameters)

I found java realtime source packages signed by ibm
- can it be useful for me (seems it replaces gc and scheduler)
- what about license in commercial project (there is no licence)