PLC to phone: machine notifications via HTTP POST

July 14, 2026 · 5 min read

The machine is done and waits for its next job – but the operator is three halls away. Andon lights and pagers stop at the factory wall. A phone doesn’t. If your PLC (or a small gateway next to it) can send one HTTPS POST, every worker’s phone becomes the signal light.

The idea

Install the Webhooky app on the workers' phones, create one endpoint per machine or per signal (“Line 3 done”, “Press fault”), and let the machine POST to it:

POST https://api.webhooky.app/MACHINE3_KEY
Content-Type: application/json

{"title": "✅ Line 3 finished", "message": "Batch 4711 done – ready for next job", "sound": "doorbell_1"}

Everyone signed in to that account gets the push – multiple phones per endpoint are the default, not an extra.

Option 1: straight from the PLC

Siemens S7-1200/1500: the LHTTP library (part of Siemens' open library ecosystem) can send HTTP requests from TIA Portal projects; HTTPS support depends on firmware/library version.
Beckhoff TwinCAT 3: the Tc3_IotBase HTTPS client (FB_IotHttpClient) sends the POST natively.
CODESYS-based PLCs (WAGO, Schneider, …): the Web Client library does the same.

Option 2: a gateway next to the PLC (recommended)

Many production PLCs can't or shouldn't speak TLS to the internet. The pragmatic pattern is a small edge device – a Raspberry Pi or industrial PC that already collects machine data – translating a PLC signal into the POST. With Node-RED this is a two-node flow:

Input node: S7-comm / OPC UA / Modbus reads the “done” bit
http request node: POST to your Webhooky endpoint with title, message and sound

This keeps the PLC program untouched and the machine network isolated – only the gateway needs outbound HTTPS.

What it replaces

Waiting operators and idle machines between jobs
SMS gateways with SIM cards and monthly fees
Pager systems and plant-wide horns for events that concern one person

Practical tips

Give faults an alarm sound and “done” signals a friendly one – operators learn to react by ear.
Use the Important setting for faults (heads-up banner on Android) and Silent for informational counters.
The in-app history doubles as a simple event log per machine.

Get Webhooky

Free for your first 100 notifications – set up your endpoint in two minutes.