How to keep an ODROID device connectable via adb?

I'm using an Odroid (rooted) device running Android 5.1.1 on a local network and I'd like to be able to control it via adb.

Currently I'm running this at startup:

setprop service.adb.tcp.port 5555

stop adbd

start adbd

This works initially, but I've noticed if works with one connection at a time.
If a connection is left open, a second connection won't work.
Even though adb says I'm connected, whenever I try to run any command I get an error:

> adb connect 192.168.0.33

connected to 192.168.0.33:5555

> adb shell date

error: device offline

What's the easiest to ensure adbd is accessible, even if a connection is left open/hanging by accident ?

I'm thinking about running a script that periodically restarts adbd but having a short interval
will be very frustrating as I'd need to constantly reconnect. Is there a way to check if a connection
is open, but hanging ? (no data has been received in a while ?)

Alternatively, would it be possible to close the previous connection if a new one is made automatically ?

How would one keep an odroid connectible via adb constantly (regardless of open connections ?)