OCPP API

    OCPP integration documentation

    Technical instructions for installers and developers to connect OCPP chargers to Joulo's Central System Management Server (CSMS).

    OCPP 1.6J
    WebSocket
    SHA-256

    // connection

    WebSocket endpoint

    URL format

    wss://ocpp.joulo.nl/cp/<charge_point_id>?auth=<security_secret>
    charge_point_idUnique ID of your charger • assigned during registration in the Joulo dashboard.
    security_secret24-digit automatically generated secret. Available in the charger panel after connection.

    // messages

    Supported OCPP messages

    BootNotification
    CP → CSMS

    Registration on connection • vendor, model, firmware

    Heartbeat
    CP → CSMS

    Periodic status check • every 60 seconds

    StatusNotification
    CP → CSMS

    Connector status: Available, Charging, Faulted

    StartTransaction
    CP → CSMS

    Start charging session with meter value

    StopTransaction
    CP → CSMS

    End session, final meter reading and reason

    MeterValues
    CP → CSMS

    Intermediate energy measurements (Wh)

    Authorize
    CP → CSMS

    User authorization • always accepted

    DataTransfer
    CP ↔ CSMS

    Vendor-specific messages

    // security

    Authentication & security

    Each charger receives a unique 24-digit security secret at registration. This secret is:

    • SHA-256 hashed in the database • the original is never stored
    • Transmitted via encrypted WebSocket (wss://)
    • Visible to the user once • can only be regenerated afterwards

    Connections without a valid secret are rejected. Every message is validated against the OCPP 1.6J schema.

    // configuration

    Configuration per brand

    OCPP settings are located in different places per brand. After connecting your charger in the Joulo dashboard, you'll receive step-by-step instructions specific to your brand.

    Web interface

    Many chargers have a built-in web server (e.g. 192.168.x.x) where you configure the OCPP URL.

    Manufacturer app

    Some brands (Alfen, EVBox) offer an app or cloud portal where you set the OCPP backend URL.

    Installer

    In some installations, the installer configures the OCPP settings during mounting.

    Related pages

    Joulo for developers

    Overview of all tools, APIs and integrations.

    OCPP connection

    Connect any OCPP 1.6J charger to Joulo.

    OCPP Proxy / Splitter

    Open-source proxy for multiple backends.

    Platform status

    Realtime status of all Joulo services.

    developer.joulo.nl

    Developer portal with extended documentation.

    status.joulo.nl

    Realtime status of all Joulo services.

    Ready to get started?

    Create a free account and connect your charger. Find your API token directly in the dashboard.

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