Fresh install on Raspberry Pi 4 fails with "Cannot GET /"

[John27long27]

Hello, I'm trying to do a fresh installation on a Raspberry Pi 4 to control my Pentair system. I'm following the standard installation steps, but after running npm start, the web page shows a "Cannot GET /" error.

Here is what I have already tried:

Confirmed the rs485Port is set correctly to /dev/ttyUSB0 in config.json.

Manually ran npm run build before npm start.

Deleted the node_modules and dist folders and ran a full npm install again.

Even after a completely clean installation, the problem persists. It seems like the web page files are not being built or served correctly.

Can you offer any advice?"

[tagyoureit]

This app, njsPC, runs on port 4200 and has API endpoints. dashPanel has the web UI and runs on port 5150.

[John27long27]

Thank you for the corrections.

The application starts and the log shows 'Configuration Complete' and I can see RS485 stats, so the communication is working. However, the dashPanel web server on port 5150 never starts, and the page cannot be reached. I have confirmed that dashPanel is enabled in my config.json file. Here is my startup log:

[email protected] start
npm run build && node dist/app.js

[email protected] build
tsc

Init state for Pool Controller
[25/07/2025, 00:51:04] info: The current git branch output is master
[25/07/2025, 00:51:04] info: The current git commit output is b8e5ef1
[25/07/2025, 00:51:04] info: Starting up SSDP server
[25/07/2025, 00:51:04] info: Server is now listening on 0.0.0.0:4200 - 192.168.0.38:4200
[25/07/2025, 00:51:04] info: Serial port: /dev/ttyUSB0 request to open successful 9600b 8-none-1
[25/07/2025, 00:51:04] info: Checking njsPC versions...
[25/07/2025, 00:51:04] info: Starting Pool System intellicenter
[25/07/2025, 00:51:04] info: Auto-backup initialized Last Backup: 1970-01-01T01:00:00.000+0100
[25/07/2025, 00:51:04] info: Found Controller Board IntelliCenter i5PS, awaiting installed modules.
INTELLICENTER MODULES DETECTED, REQUESTING STATUS!
[25/07/2025, 00:51:06] info: Initializing Nixie Controller
Checking IntelliCenter configuration...
[25/07/2025, 00:51:06] info: Nixie Controller Initialized
[25/07/2025, 00:51:06] info: Requesting IntelliCenter configuration
[25/07/2025, 00:51:06] info: Queued 4 configuration items
RS485 Stats:{ "bytesReceived": 229 "success": 8, "failed": 1, "bytesSent": 25, "collisions": 4, "failureRate": 11.11% }
[25/07/2025, 00:51:07] info: Configuration Complete
^CShutting down open processes
[25/07/2025, 00:51:44] info: Shut down sys (config) object timers
Stopping sys
[25/07/2025, 00:51:44] info: State process shut down
[25/07/2025, 00:51:44] info: Serial Port 0 - /dev/ttyUSB0 has been closed.
[25/07/2025, 00:51:44] info: Successfully closed portId 0 for serial port /dev/ttyUSB0
[25/07/2025, 00:51:44] info: Closed all serial communications connection.
[25/07/2025, 00:51:44] info: Shut down MDNS Server mdns
[25/07/2025, 00:51:44] info: Stopped SSDP server: ssdp
[25/07/2025, 00:51:46] info: Stopping logger Process.
Logger Process Stopped

Thank you for any help you can provide.

[tagyoureit]

dashPanel is a separate application. You need to follow the link I previously provided and install it. Run that in a separate terminal window/session until you get this all running (see below).

^CShutting down open processes

You also need to keep this app running. See this page in the wiki for that. You can absolutely run it from the command line for now, but eventually you will want the app to run without a user needing to be logged in.

[John27long27]

Thank you for the help! I am able to get everything up and running but once I run the pm2, I start having connection issues. Details below, any suggestions?

The njsPC backend and dashPanel frontend work perfectly when I run them manually in separate terminals using npm start. However, when I manage dashPanel with pm2, the service shows a status of online, but I cannot connect from a browser and get an ERR_CONNECTION_REFUSED error.

What Works:

njsPC connects to my IntelliCenter panel and the log shows "Configuration Complete."

dashPanel loads and is fully functional at http://:5150 when I run npm start manually.

What Fails:

When dashPanel is started via pm2, the browser connection is refused.

The pm2 logs dashPanel command shows that the log files are empty, indicating the app is crashing silently and getting stuck in a restart loop.

My pm2 Status (shows everything "online"):

┌────┬───────────┬───────────┬────────┬──────┬───────┬────────┬───┬──────────┬──────┬─────────┬────────┬──────────┐
│ id │ name │ namespace │ version│ mode │ pid │ uptime │ ↺ │ status │ cpu │ mem │ user │ watching │
├────┼───────────┼───────────┼────────┼──────┼───────┼────────┼───┼──────────┼──────┼─────────┼────────┼──────────┤
│ 1 │ dashPanel │ default │ 8.1.1 │ fork │ 4401 │ 0s │ 3 │ online │ 0% │ 25.1mb │ jgi… │ disabled │
│ 0 │ njsPC │ default │ 0.39.7 │ fork │ 3067 │ 64m │ 0 │ online │ 0% │ 63.4mb │ jgi… │ disabled │
└────┴───────────┴───────────┴────────┴──────┴───────┴────────┴───┴──────────┴──────┴─────────┴────────┴──────────┘
My ecosystem.config.js file for dashPanel:

JavaScript

module.exports = {
apps : [{
name : "dashPanel",
script : "dist/app.js"
}]
}
My Environment:

Device: Raspberry Pi 4

OS: Debian (Raspberry Pi OS)

Node.js Version: v22.17.1 (installed via nvm)

Any suggestions would be greatly appreciated. Thank you!

[tagyoureit]

There's an entire PM2 ecosystem.config.js file in the Wiki you should start with. pm2 monit is also your friend for looking at the logs.

[John27long27]

Thank you again for all the help! It is up and running now, no issues.

[raidflex]

What did you do to fix the issue. I am having a similar issue where I can start njsPC server manually but when I use pm2 it keeps crashing?

I see this error in the logs. I also double checked my ecosystem.config.js file is pointing to the correct directory.
The dashPanel and Relay manager start up without issues.

[tagyoureit]

Pull again. I pushed a bad build for this error.