…and how to “fix” it
Ubiquiti’s Discovery Tool hasn’t seen an update since 2017 — and if you try running it on a modern system, you’ll probably get this very helpful error:
A Java Exception has occurred.
That’s it. No stack trace, no details, just failure.
Installing an ancient Java version system-wide isn’t exactly great for security, so here’s how I got it running safely on a modern setup – without downgrading my main Java install.
Why it fails
The Discovery Tool was built for Java 8, and newer Java versions have changed how modules and class paths work.
So when you double-click the old launcher, it tries to call methods that no longer exist — hence the opaque “Java Exception” message.
The fix
Here’s the approach that worked for me.
First, I downloaded the Ubiquiti Discovery Tool – the same old 2017 version.
Then, I grabbed JRE 8u271, the tar.gz archive version, not the installer.
I extracted both archives into the same directory, then opened the batch file that launches the Discovery Tool in my favourite text editor.
Inside the .bat, I replaced the hardcoded Java path with the one pointing to the javaw.exe inside my local JRE directory.
That ensures that the Discovery Tool runs with Java 8 only in that folder, without affecting system Java installation.
And that’s it – double-click the batch file again, and voilà:
Why this is safer
This approach keeps the old Java runtime isolated from the rest of your system.
You’re not downgrading or overwriting your installed Java – just using the correct version locally where it’s needed.
Alternatives
If you only use the Discovery Tool to find device IPs, there are alternatives – but none quite as convenient.
The newer UniFi Network Application and UISP can discover devices too, but both are server applications meant for full network management. They’re far more complex to set up and run than this little Java utility.
If all you need is to locate devices on your LAN, a simple nmap scan or a mobile network discovery app will get you there faster — no Java, no setup, no fuss.
Closing thought
Pretty poor show, Ubiquiti – leaving a core utility broken for years and still available for download.
At least it’s fixable. With a bit of old-school hackery, this tool still runs just fine in 2022 and the foreseeable future.
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