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Another device using the same IP address on System 7.6.1 after running my app.

So I finally got my app running on 68k, two network requests succeeded as I saw content in the window, then when I began typing I got this error saying that another device was using my IP address... I should note I am using a blueSCSI with Open Transport which has been working perfectly with iCab etc, but it seems my app screwed it up somehow and I am not sure how to reset it back to a working configuration. Neither my app nor iCab works anymore it just throws this error. Any ideas on how to reset? I have tried setting the TCP/IP prefs back, deleting prefs entirely and reconfiguring, rebooting of course... I am also looking for any ideas about why my app could have screwed it up in the first place after using the network successfully a couple of times.

It is a Code Warrior PowerPlant based app, compiled for 68k on a PPC PowerBook G3 running Mac OS 8.6. The app works fine on the PowerBook using the laptops real ethernet port.

Screenshot 2024-04-07 at 10.33.16 AM.png


Well-known member
Is that actually the MAC address of your Mac? The simplest suggestion here is that your router has screwed up and actually given the same IP address to two things...
How would I find my MAC address? Would it be the address of the Pico device in the BlueSCSI? Or should I be looking into my WiFi router. It’s just odd that my app could have caused this. Seems unlikely a coincidence


Well-known member
pi pico devices tend to have MAC addresses in the Raspberry Pi OUI.

your best hope is that your router's UI has a MAC address table that will help you track down the errrant device.

while I am loath to rule anything out as the impact of a possible software bug, unless your software has done something incredibly naughty, I would be looking at the infrastructure first.

in general, if you are going to be developing network-facing applications, it is a good idea to have at least a managed switch upstream of the thing you're developing/testing on.


Well-known member
Do you have another BlueSCSI on you network? You can check the MAC address in your BlueSCSI configuration file.
Thanks for all this info - I’m currently trying to log into my router, when frogfind decided to load. I had unplugged a google mesh extender that failed to set up and was closest to the blueSCSI… still no idea what broke it or fixed it. Will run my app again and see if it screws it up again.

I am ignoring an orderly disconnect exception in my code because I couldn’t work out how to catch it, that’s all I can think of from my end that could cause it. That doesn’t seem too naughty though!
The app is working fine now, must have been the router for sure that righted itself once I unplugged the mesh network?

Anyway I’m typing away happily in my Notion app and it’s sending edits to the server from my LCIII ❤️


Well-known member
A lot of the time just resetting the router will temporarily fix this.

Another solution (which I finally employed on my network when I had similar issues), is to have the router assign a static IP to each device based on their MAC address. That way, the router physically cannot assign the same IP to two devices...and they also will always have the same one. You just need to get the MAC address of each device and adjust your router to do it.


Well-known member
I usually try to get the device IP first. I connect it to my known working Powerbook G4 with Tiger, hardwired through ethernet cable, then allow WIFI internet sharing "through ethernet". Usually all older machines get detected and a correct IP addressed. Then I can use the IP for manual connection in TCP/IP.