Thank You very much for Your efford!

I'll give it a try...

Because system the script will run is an alix-hardware with openWrt it's quite hard to install fancy modules.

Luckily select does not wait too busy if timeout is > 0.

time perl Inet.Server6.pl 
0 Active connections
0 Active connections

real    1m1,987s
user    0m0,023s
sys     0m0,013s
[download]

Well, if i play with this script and two instances ofcat - | nc -q 1 localhost 5000 the second line seems to vanish if the other instance is blocking the IO.
I have no data-loss if the read-size is large enough and with non-blocking IO.