Open Source

MIT License

TypeScript

OCPP Proxy / Splitter

Route your charger's OCPP traffic to multiple backends simultaneously. Keep your original CSMS and connect to Joulo — or any other platform.

View on GitHub Quick Start

// Architecture

One proxy, multiple backends

The proxy sits between your charger and the backend(s). Your primary CSMS retains full control — including sending commands back. Secondary backends receive a read-only copy of all messages.

⚡ Charger (OCPP)

│

▼

🔀 Joulo OCPP Proxy

│▼

Primary CSMS

full control

│▼

Secondary CSMS

read-only mirror

┆▼

CSMS N…

read-only mirror

Charger → CSMS

Messages are forwarded to the primary CSMS and mirrored to all secondary backends.

CSMS → Charger

Only the primary CSMS can send commands back to the charger. Responses from secondary backends are ignored.

// Features

Everything you need

Split & Mirror

One incoming connection, multiple backends. Primary CSMS has full control, secondaries receive read-only copies.

Auth forwarding

HTTP Basic Auth credentials are automatically forwarded to all upstream backends.

Sub-protocol negotiation

Automatic negotiation of OCPP 1.6, 2.0 and 2.0.1 sub-protocols.

Docker-ready

Pre-built images on GitHub Container Registry. One command to start.

Lightweight

TypeScript/Node.js, minimal footprint. Runs as non-root user in Docker.

Structured logging

JSON logs to stdout/stderr. Set LOG_LEVEL=debug to see individual OCPP messages.

// Quick Start

Up and running in 3 steps

Docker (recommended)

docker run -d \
  -p 9000:9000 \
  -e PRIMARY_CSMS_URL=wss://your-primary-csms.example.com/ocpp \
  -e SECONDARY_CSMS_URLS=wss://analytics.example.com/ocpp \
  ghcr.io/joulo-nl/joulo-ocpp-proxy:main

Docker Compose

git clone https://github.com/joulo-nl/joulo-ocpp-proxy.git
cd joulo-ocpp-proxy
cp .env.example .env
# Edit .env with your CSMS URLs
docker compose up -d

From source

git clone https://github.com/joulo-nl/joulo-ocpp-proxy.git
cd joulo-ocpp-proxy
npm install
npm run build
PRIMARY_CSMS_URL=wss://your-csms.example.com/ocpp npm start

// Configuration

Environment variables

Variable	Required	Default	Description
PORT	No	9000	Port the proxy listens on
PRIMARY_CSMS_URL	Yes	—	WebSocket URL of your primary CSMS
SECONDARY_CSMS_URLS	No	—	Comma-separated list of secondary CSMS URLs
LOG_LEVEL	No	info	debug, info, warn, or error

// Charger setup

Point your charger to the proxy

Change the OCPP backend URL in your charger's settings:

Before:wss://your-csms.example.com/ocpp/CHARGER-001

After:ws://proxy-host:9000/CHARGER-001

The proxy appends the charge point ID from the incoming URL to each upstream CSMS URL automatically.

// Use cases

When would you use this?

Multi-backend monitoring

Run your chargers against your primary platform while mirroring data to your own analytics or energy management system.

Platform migration

Mirror traffic to the new platform and verify it processes messages correctly before switching over.

Development & debugging

Mirror production charger traffic to a local development CSMS for testing without affecting the live system.

Compliance & auditing

Send a copy of all OCPP messages to an audit system for regulatory compliance.

Joulo for developers

Overview of all tools, APIs and integrations.

OCPP connection

Connect any OCPP 1.6J charger to Joulo.

REST API

API documentation, endpoints and Home Assistant.

Platform status

Realtime status of all Joulo services.

developer.joulo.nl

Developer portal with extended documentation.

status.joulo.nl