Wi-fi in Access Point mode

[Steph]

Well Steph,

I don't know if it is possible with netPI since it does not support port forwarding. But as I said before I am no networking expert.

I analysed your PDF. Supposing you connect you Wifi tablet to the netPI Wifi access point ...  then it would get an IP address in the range from 17.100.4.80 to 89. 

In the most simpliest case it would get the first ip address 17.100.8.80 through netPI's Wifi DHCP server, right? Also your Wifi tablet should automatically receive a gateway address through the same netPI Wifi DHCP server. Which one is it? Is it 17.100.8.16 which is the Wifi IP address of netPI? The gateway address in your tablet is the first most relevant value to know to let the routing table in your tablet know where to send a ping to e.g. 192.168.1.100 to. Cause any IP address that is not in any known subnet will be sent to the default gateway which must be the netPI IP address. Else not even the ping ethernet frame is leaving your tablet at all.

Thx
Armin

Dear Armin,

everything works now as I want it to work.

You reminded me to eliminate my standard gateway of my other ethernet interface on my PC (off course not necessary on my tablet, because it does not has a standard gateway).
In adddition, it seems that the netPI deactivates eth0 if nothing is connected to it so I could not reach it, before I connected it to a network.
And in my PLC (an S7-1516) I had also to configure to use a router for the interface and the router address has to be the address of eth0 of the netPI. 

After connecting to the WLAN of the netPI I can now ping wlan0 and eth0 of the netPI as well as the ethernet interface of my PLC.

So now I can reach the OPC UA-Server on the PLC out of nod-red on the netPI as well as out of an OPC UA Client on my tablet. I can reach node-red from the netPI and the dasboards from my browser in the tablet. I can also reach the webserver of my PLC out of a browser on the tablet. Additionally, which was not needed, I can reach all from my PC.
It sounds a bit redundant but this is for didactic reasons.

Thanks a lot
  Stephan