How to listen to a UDP port?

[SkipperEarly]

To share data, devices must be in the same network and since your windvane can only work as an access point you need to connect OP to him. Connect the same way as you connect with your ipad.
Then you can define the UDP connection adding a network connection in NMEA 0183 tab. See the "Type" field.
If you want OP to work as an access point too, you need another wifi dongle and set the access point with this device.

 Thanks Sailoog for swift reply.
Understand the issue of my device being only AP and therefore needing additional wlan dongle, thats exactly what I want.
I receive the wind data over wlan1 and distribute them (together with GPSdata, AIS etc) over wlan0(10.10.10.1:10110)


I am working headless with VNC on my PC and when I select connect wlan on the gui, I sometime see/sometimes not see the windvane network. I even put the raspi next to the wlan AP and have all devices on reliable power!
when visible I select the windvane network (it has a transmitter-mast-icon next to it) and then it runs long in a loop, disconnecting / reconnecting also the VNC connection. After approx 1 Minute still no connection is established and I am not given the option to configure in OP NMEA tab the connection, I know have set the type to UDP but I do not have the IP address just the SSID of the network. 
From the connection on the iPad I detected  that the DHCP has address 169.254.193.188 (255.255.0.0) but on network info it doesnt show a client IP, dont know why.

As stated its very cumbersome to test with VNC as I have to switch always networks on the PC. To use VNC on the iPad I can only view as I have not managed to switch the virtual keyboard on within VNC (doubble tapping on a text field doesnt work)

Will try tomorrow again with a HDMI screen.

Thanks for advise.