Connecting to your CPMS
The emulator connects to any OCPP-compliant backend over WebSocket. This guide covers the connection details and the most common failures.
Connection URL
OCPP-J uses the charge point identity as the final path segment:
wss://your-cpms.example.com/ocpp/<charge-point-id>
Use wss:// (TLS) in any environment that isn't local development.
Subprotocol negotiation
The charger offers an OCPP version via the WebSocket Sec-WebSocket-Protocol
header (e.g. ocpp1.6). Your CPMS must echo the selected subprotocol back, or
compliant clients will close the connection.
Security profiles
| Profile | Transport | Auth |
|---|---|---|
| 1 | TLS | HTTP Basic |
| 2 | TLS | HTTP Basic + server cert |
| 3 | mTLS | Client certificate |
Match the profile your CPMS expects; a mismatch shows up as a failed handshake before any OCPP message is exchanged.
Troubleshooting
- Immediate close after connect — usually a missing/echoed subprotocol or a
rejected
BootNotification. - Connects then goes silent — check the negotiated
HeartbeatInterval; the CPMS may be dropping idle sockets. - 401 on connect — Basic auth credentials don't match the charger identity.
Next steps
Once connected, follow Simulating a charger to drive a full session.