OCPP 1.6J Simulator & Emulator: Every Core Message

OCPP 1.6J in a nutshell

In OCPP 1.6J the charge point keeps one WebSocket open to the Central System and both sides send CALL frames that the other answers with a CALLRESULT or CALLERROR. Transactions are bracketed by StartTransaction and StopTransaction, and energy is reported in between with MeterValues.

// Charge point → CSMS  (CALL: [2, uniqueId, action, payload])
[2, "8f3a", "BootNotification", {
  "chargePointVendor": "Elmo",
  "chargePointModel": "Virtual-Emulator-1"
}]

// CSMS → charge point  (CALLRESULT: [3, uniqueId, payload])
[3, "8f3a", {
  "status": "Accepted",
  "currentTime": "2026-09-29T10:00:00Z",
  "interval": 300
}]

// Later, during a transaction
[2, "91c2", "MeterValues", {
  "connectorId": 1,
  "transactionId": 1001,
  "meterValue": [{
    "timestamp": "2026-09-29T10:05:00Z",
    "sampledValue": [
      { "measurand": "Energy.Active.Import.Register", "value": "4500", "unit": "Wh" },
      { "measurand": "SoC", "value": "15.0", "unit": "Percent", "location": "EV" }
    ]
  }]
}]

Messages the simulator sends

BootNotification, Heartbeat, StatusNotification, Authorize, StartTransaction, MeterValues, StopTransaction, DataTransfer, DiagnosticsStatusNotification, FirmwareStatusNotification, SecurityEventNotification and LogStatusNotification — plus any other action with a custom payload from the built-in message composer.

CSMS commands it answers

• Remote control

  RemoteStartTransaction, RemoteStopTransaction, Reset, UnlockConnector, ChangeAvailability, TriggerMessage.

• Configuration

  GetConfiguration and ChangeConfiguration, with read-only keys rejected as a real charger would.

• Reservations and authorization

  ReserveNow, CancelReservation, SendLocalList, GetLocalListVersion, ClearCache.

• Smart charging

  SetChargingProfile, ClearChargingProfile, GetCompositeSchedule.

• Firmware and diagnostics

  UpdateFirmware and GetDiagnostics run their full status sequences; SignedUpdateFirmware and GetLog from the security extension.

• Certificates and data transfer

  InstallCertificate, DeleteCertificate, GetInstalledCertificateIds, CertificateSigned, ExtendedTriggerMessage, DataTransfer.

Connecting to your Central System

1. Set the CSMS URL, for example ws://localhost:9000. The charge point ID is appended to the path when connecting.
2. Pick OCPP 1.6J. Use a wss:// URL if your server requires TLS.
3. Select Connect. After an accepted BootNotification the simulator sends heartbeats at the interval your CSMS returned.

Moving to the newer protocol? The OCPP 2.0.1 simulator guide covers what changes.