If both of your server and client are deployed on Linux 3.7+, you can turn on fast_open for lower latency.
First set fast_open to true in your config.json.
Then turn on fast open on your OS temporarily:
echo 3 > /proc/sys/net/ipv4/tcp_fastopen
To turn on fast open permanently, see Optimizing Shadowsocks.
Notice: only some versions support this feature.