Ok, after days I got the solution (without socat).
For all of the german guys, please read here: Razberry7 testen (ohne OH) - openhabforum.de
For all others, just let me pronounce that it was a failute in too many linebreaks inside ser2net.yaml
Here a working configuration:
define: &banner \r\nser2net port \p device \d [\B] (Debian GNU/Linux)\r\n\r\n
connection: &aeotecstick7
accepter: tcp,4000
enable: on
options:
banner: *banner
kickolduser: true
telnet-brk-on-sync: true
connector: serialdev,/dev/serial/by-id/usb-Silicon_Labs_CP2102N_USB_to_UART_Bridge_Controller_5828e4a40755ed1186a193131d62bc44-if00-port0,115200n81,local
connection: &razberry7
accepter: tcp,4001
enable: on
options:
banner: *banner
kickolduser: true
telnet-brk-on-sync: true
connector: serialdev,/dev/ttyAMA0,115200n81,local
connection: &ender3pro
accepter: tcp,5000
enable: on
options:
banner: *banner
kickolduser: true
telnet-brk-on-sync: true
connector: serialdev,/dev/serial/by-id/usb-1a86_USB2.0-Serial-if00-port0,115200n81,local
Should then look like that:
root@zwave:~# lsof -i
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
...
ser2net 3443 root 7u IPv6 27543 0t0 TCP *:4000 (LISTEN)
ser2net 3443 root 8u IPv6 27544 0t0 TCP *:4001 (LISTEN)
ser2net 3443 root 9u IPv6 27545 0t0 TCP *:5000 (LISTEN)
ser2net 3443 root 10u IPv6 27546 0t0 TCP 192.168.1.14:4000->192.168.5.203:48282 (ESTABLISHED)
ser2net 3443 root 12u IPv6 27547 0t0 TCP 192.168.1.14:4001->172.17.0.2:40624 (ESTABLISHED)
ser2net 3443 root 14u IPv6 29343 0t0 TCP 192.168.1.14:5000->192.168.1.111:39644 (ESTABLISHED)