Just some other tips:
My configuration only worked when i added echo=0 to the configuration.
So from
pty,link=/dev/ttyUSB0,raw,user=openhab,group=dialout,mode=777 tcp:172.16.11.5:3333
to
pty,link=/dev/ttyUSB0,raw,echo=0,user=openhab,group=dialout,mode=777 cp:172.16.11.5:3333
Also with the newer versions of ser2net, you can make multiple connections to one serial port by adding max-connections=N to the configuration. For the dutchies this might be handy when using a DSMR data logger and a seperate OpenHAB instance.
Just for reference, my ser2net line is
3333:raw:0:/dev/ttyUSB-P1:115200 8DATABITS NONE 1STOPBIT max-connections=3
Ser2net is downloadable from https://sourceforge.net/projects/ser2net/