Docker exposed port don't send data on eth0

[COswald]

Hello Armin,

I have an issue, that is hard to descript. 

Base is a NIOT-E-TPI51-EN-RE.
Eth0 is configured as DHCP and working, I can connect to the Portainer and Control Panel from the outer netwerk to this IP-Address
On this box Docker is enabled
First Container is a hilschernetpi/netpi-netx-ethernet-lan image, which enables the cifx0 as 'normal' Ethernet-Port.

cifx0 is configured as
- IP-Address: 192.168.1.1
- SUBNET: 255.255.255.0
- Gateway: 192.168.1.1
- DNS: 9.9.9.9

In the Docker a second Container which if from image hilschernetpi/netpi-raspbian is running a node script to build a OPC UA server.
This Container exposes the following ports
remote 2222: local 22 --> SSH
remote 4334: local4334 --> opc.tcp

I can access the SSH port of the second container (2222) from eth0 and cifx0 without any problems
opc.tcp (4334) is available from cifx0, but if I try to connect from eth0 I cannot get a connection. A ping on that port is working, but i don't get data.

Firewall settings
eth0: NAT-Trusted
cifx0: Trusted (default)

Routes:
- no routes defined -

I do not see the error, but I'm sure it is just in front of my eyes.

Can you give me a hint?

Kind regards,

Carsten