TCP Basics - if you want to implement a command/reply protocol you have to set TCP_NODELAY.

This is doubly so when using Netty and abstractions on top of it which form the full command (or response) in one write buffer to write out. In such double-buffering environments the additional buffering in the kernel which happens when not setting NO_DELAY makes no sense and can only do harm in terms of latency.

References (I can probably start with TCP Illustrated here):

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_MRG/1.2/html/Realtime_Tuning_Guide/sect-Realtime_Tuning_Guide-Application_Tuning_and_Deployment-TCP_NODELAY_and_Small_Buffer_Writes.html

or

http://www.techrepublic.com/article/tcp-ip-options-for-high-performance-data-transmission/

and even the (reference) ssh implementation. Quoting from the source of openssh:

if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof opt) == -1)
error("setsockopt TCP_NODELAY: %.100s", strerror(errno));

Patch to follow shortly.