NetworkInterface command causes exception

Targets Raspberry Pi
1

Hello all,

In a RPi console app under Xojo 2022 R3.2 running in Buster in an RPi4 8Gig device the following code results in an exception.

Dim n As NetworkInterface = System.NetworkInterface(0)

I have also tried Dim n As NetworkInterface = System.NetworkInterface(1) too and have limited the connection to Ethernet only, from both Ethernet and WiFi. Also tried in Xojo 2019R1.1

Dim n as NetworkInterface //= System.GetNetworkInterface(0)

Same result. What am I doing wrong???

Edit
Perhaps I am not waiting long enough to run this - it is started by a systemd service. On boot it fails at the spot written above, but if I run the systemd command after boot then it starts fine without errors…

Thanks
Tim

2

Make sure your service has the network set as a prerequisite. That should fix this.

Probably

After=network-online.target

3

you could look if your network is listed before you access any index?

For i As Integer = 0 To System.NetworkInterfaceCount - 1
Next

https://documentation.xojo.com/api/networking/networkinterface.html

at pi3 menu settings / raspberry pi settings there was a checkbox
network at boot: wait for network

4

Hi Guys,

@Greg, I tried adding that - no go. I already had some wait statements but this addition did not help…
Here’s what I have for the systemd script:

[Unit]
Description=Axcys Client Service
#After=NetworkManager-wait-online.service network.target network-online.target dbus.service
#Wants=NetworkManager-wait-online.service network-online.target
#systemctl enable axcys-client-service.system

After=sockets.target
After=network.target
After=postsgresql.service
After=network-online.target debus.service
After=network-online.target

#After=axcys-embedded-engine.service
RestartSec=5

[Service]
Type=simple
#Type=forking
ExecStart=/home/pi/Public/axcys/AxcysClientService/axcysclientservice

Restart=always

[Install]
WantedBy=multi-user.target

Any other ideas?
Tim

5

Make sure you also add the

Requires=network-online.target

Because After doesn’t “imply a relationship” apparently.

Reading the Unit File docs, I get the impression that After merely means that your service is started after the network-online service starts, but that it may be that it hasn’t actually reached a working state yet. Having code to periodically check to see if the network is available and try again in a few seconds may be the right thing to do anyway. I know we tackled this for Xojo Cloud, but I can’t remember what the solution was unfortunately, but it may have been the support of the watchdog protocol that ultimately fixed it.

6

Hi Greg,

That’s what I did - I wrote code to manage this so that it can start anytime I periodically check for a connection, but it is running. This definitely solved the problem. It was something that was not really apparent when I originally wrote this little app a few years ago, using my Windows machine - there was not waiting, as it was always there!

Thank you again for your help!
Tim