OCPP

OCPP (Open Charge Point Protocol) is how an EV charging station talks to its CSMS, the Charging Station Management System of a charge point operator (in OCPP 1.6, the Central System). The station opens a WebSocket to the CSMS with its own identity in the URL, and from then on either side sends requests: the station boots, authorizes a card, reports a transaction and sends meter values; the CSMS starts and stops sessions remotely, limits power, reads and changes configuration, and updates firmware. Messages are JSON, and the Open Charge Alliance publishes a JSON schema for every one of them.

Where you meet it

• Public and workplace charging networks run by charge point operators
• Home and fleet chargers managed by an energy management system or an aggregator
• Smart charging: limiting the power of a station or a whole site to what the grid connection allows

Quickstart

From the command line

Download ocppctl from GitHub Releases. No CSMS at hand? Start one:

ocppctl server start --insecure-transport --no-auth

and talk to it from another terminal:

# Which OCPP version does the CSMS pick?
ocppctl client probe --url ws://localhost:9000/CS001 --insecure-transport

# Register the station: Accepted, Pending or Rejected?
ocppctl client boot --url ws://localhost:9000/CS001 --insecure-transport

# A simulated station that stays connected and charges by itself
ocppctl client run --url ws://localhost:9000/CS002 --insecure-transport

# From the CSMS side: list the stations and start a session on one
ocppctl server stations
ocppctl server call RequestStartTransaction --station CS002 --yes \
  --payload '{"remoteStartId":1,"idToken":{"idToken":"TESTTOKEN","type":"ISO14443"}}'

A real CSMS uses TLS: --url wss://csms.example.com/ocpp/CS001 with a password from --password-file (security profile 2), or a client certificate (profile 3).

From Go

go get github.com/otfabric/go-ocpp

A CSMS that accepts every boot, and a charging station that connects to it (OCPP 2.0.1, abridged from the go-ocpp README):

// CSMS: answer the stations' CALLs.
type csms struct{ ocpp201.UnimplementedCSMSHandler }

func (csms) BootNotification(ctx context.Context, p ocpp.Peer, req *ocpp201.BootNotificationRequest) (*ocpp201.BootNotificationResponse, error) {
  return &ocpp201.BootNotificationResponse{Status: ocpp201.RegistrationStatusAccepted, CurrentTime: time.Now().UTC(), Interval: 300}, nil
}

srv, err := server.New(
  server.WithHandler(ocpp.V201, ocpp201.CSMS(csms{})),
  server.WithAuthenticator(server.BasicAuth(lookupPassword)),
)
http.Handle("/ocpp/", srv) // behind TLS

// Charging station.
c, err := client.New("wss://csms.example.com/ocpp/STATION001",
  client.WithHandler(ocpp.V201, ocpp201.ChargingStation(station{})),
  client.WithBasicAuth("STATION001", password),
  client.WithReconnect(client.DefaultReconnect()),
)
err = c.Connect(ctx)
boot, err := ocpp201.BootNotification(ctx, c, &ocpp201.BootNotificationRequest{
  Reason:          ocpp201.BootReasonPowerUp,
  ChargingStation: ocpp201.ChargingStationType{VendorName: "Example", Model: "TestStation"},
})

Every request is validated against its OCA schema before it is sent, every response when it arrives, and every incoming request before a handler sees it.

What go-ocpp and ocppctl support