Is OSC TCP Packet Length Mode broken

I have problems with TCP connection using Packet Length OSC 1.0
I tried with TouchOSC on macOS and it doesn't work, also with an experimental Arduino Opta.
With my Arduino Opta application I can send only one packet then my application is broken cause the network socket is blocked however.
So I tried with TouchOSC and have also no luck.
SLIP works without a problem on both applications.