I want to connect 8 wires (5V) that meets in some box where I have ethernet cable (LAN) to RaspPI with openhab over LAN (because it is in another place than this box). I need some bridge/board where I could wire those 8 pins and establish communication to openhab in the easiest way
At the beginning I wanted to add another Raspberry PI but actually there must be something simpler
EDIT: it seems that good solution would be to use MQTT Arduino + enc28J60, but maybe anyone knows something already on one board?
Bartosz, it is a bit unclear to me what you exactly want.
Do I understand correct you have signals from 8 cables that you want to transfer to openhab and that the closest connection is a box with an ethernet cable?
Is the other end of that ethernet cable plugged into yr router or yr raspberry?
If the other end it is in your router then yes an Arduino+enc28J60 is a possibility but keep inmind that that leaves you little room for programming, but if it is just to relay the state of a cable it should be OK. But it might be better to take a W5100 or W5500 instead of a 28J60. if you want ‘everything on one board’ that depends a bit what ‘everything’ is, but a shield would be a better option than an ethernet module
However, if you meant you have an UTP cable from your ‘box’ going to your raspi, then I would suggest to use that cable to connect to your gpio pins.
If you can clarify what exactly you want, I might be able to give a better/more to the point reply
Do I understand correct you have signals from 8 cables that you want to transfer to openhab and that the closest connection is a box with an ethernet cable?
Yes.
Is the other end of that ethernet cable plugged into yr router or yr raspberry?
The ethernet cable is connected to the router.
I have ordered few minutes ago W5100 shield + Arduino UNO, with MQTT communication it should work. I will 3d print some cover so that it will looks like “one board” I wanted to have 
Thx for Your help!
in that case indeed an aruino with w5100 shield would be yr best option. There might be an arduino with ethernet on one board, but that is probably more expensive
