@AWI @Hoffan @sundberg84
I can see both sketches are working, this is what the gateway prints out:

0;0;3;0;14;Gateway startup complete.
0;0;3;0;9;read: 105-105-0 s=255,c=0,t=18,pt=0,l=5:1.5.1
105;255;0;0;18;1.5.1
0;0;3;0;9;read: 105-105-0 s=255,c=3,t=6,pt=1,l=1:0
105;255;3;0;6;0
0;0;3;0;9;read: 105-105-0 s=255,c=3,t=11,pt=0,l=5:Relay
105;255;3;0;11;Relay
0;0;3;0;9;read: 105-105-0 s=255,c=3,t=12,pt=0,l=3:1.0
105;255;3;0;12;1.0
0;0;3;0;9;read: 105-105-0 s=1,c=0,t=3,pt=0,l=0:
105;1;0;0;3;
0;0;3;0;9;read: 105-105-0 s=2,c=0,t=3,pt=0,l=0:
105;2;0;0;3;
0;0;3;0;9;read: 105-105-0 s=3,c=0,t=3,pt=0,l=0:
105;3;0;0;3;
0;0;3;0;9;read: 105-105-0 s=4,c=0,t=3,pt=0,l=0:
105;4;0;0;3;

Is this correct?

@Hoffan I am using OpenHAB as automation on a Raspberry PI 2B and connected to a Arduino Nano.
Next to that multiple (wireless) Nano's. The Nanos are connected with a serial gateway, atleast thats whats I am trying to achieve

How to find out what the ChildIDs are of the relays? Or is this just guessing?

@AWI

As said, I've uploaded the gateway code and received this: 0;0;3;0;14;Gateway startup complete
And I uploaded the http://www.mysensors.org/build/relay sketch to the other arduino, only changed the number of relays in the sketch. This is what I got from the relay sketch:

find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
repeater started, id=105, parent=255, distance=255
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:
find parent
send: 105-105-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,st=bc:

@AWI

I do have one arduino nano for the gateway, which is connected to my raspberry pi with the openHAB server. And furthermore I have four arduinos that I can use as nodes to connect sensors and relays to.

Thanks for the fast reply!

At this point I have my arduino nano with the mysensors serial gateway sketch uploaded to it and I have a 4 relayboard connected to the arduino. As I said, i'm new to Arduino programming and such. So the first question is, what to do next? Upload that relay code and include the code you sent?

Hello all, as a newbie in the world of arduino's i've been messing with the serial gateway for a while now and i'm kinda stuck. Whatever I try, I just can't get the sensors and relays to work on the arduino nano with the serial gateway. Can anyone help me out? I am not sure how to assign those sensors and relays to childIDs. It probably isn't all too hard.. if you know how it works .