emqx4.3/apps/emqx_gateway_ocpp/README.md

emqx-ocpp

OCPP-J 1.6 Gateway for EMQX that implement the Central System for OCPP-J protocol.

Treat Charge Point as Client of EMQX

In EMQX 4.x, OCPP-J Gateway implement as a protocol Plugin and protocol Module (enterprise only).

All Charge Point connected to OCPP-J Gateway will be treat as a normal Client (like MQTT Client) in EMQX, you can manage it in Dashboard/HTTP-API/CLI by charge point identity.

The Client Info mapping in OCPP-J Gateway:

• Client ID: presented by charge point identity.
• Username: parsed by the username field for HTTP basic authentication.
• Password: parsed by the password field for HTTP basic authentication.

Charge Point Authentication

As mentioned in the ocpp-j-1.6 specification, Charge Point can use HTTP Basic for authentication. OCPP-J Gateway extracts the username/password from it and fetches an approval through EMQX's authentication hooks.

That is, the OCPP-J Gateway uses EMQX's authentication plugin to authorize the Charge Point login.

Message exchanging among Charge Point, EMQX (Central System) and Third-services

                                +----------------+  upstream publish  +---------+
+--------------+   Req/Resp     | OCPP-J Gateway | -----------------> | Third   |
| Charge Point | <------------> | over           |     over Topic     | Service |
+--------------+   over ws/wss  | EMQX           | <----------------- |         |
                                +----------------+  dnstream publish  +---------+

Charge Point and OCPP-J Gateway communicate through the specifications defined by OCPP-J. It is mainly based on Websocket or Websocket TLS.

The OCPP-J Gateway publishes all Charge point messages through EMQX, which are called Up Stream. It consists of two parts:

• Topic: the default topic structure is ocpp/${clientid}/up/${type}/${action}/${id}

  • ${clientid}: charge point identity.
  • ${type}: enum with request, response, error
  • ${action}: enum all message type name defined ocpp 1.6 edtion 2. i.e: BootNotification.
  • ${id}: unique message id parsed by OCPP-J message

• Payload: JSON string defined ocpp 1.6 edtion 2. i.e:

  {"chargePointVendor":"vendor1","chargePointModel":"model1"}
  

The OCPP-J Gateway receives commands from external services by subscribing to EMQX topics and routing them down to the Charge Point in the format defined by OCPP-J, which are called Down Stream. It consists of two parts:

• Topic: the default topic structure is ocpp/${clientid}/dn/${type}/${action}/${id}

  • The values of these variables are the same as for upstream.
  • To receive such messages, OCPP-J Gateway will add a subscription ocpp/${clientid}/dn/+/+/+ for each Charge point client.

• Payload: JSON string defined ocpp 1.6 edtion 2. i.e:

  {"currentTime": "2022-06-21T14:20:39+00:00", "interval": 300, "status": "Accepted"}
  

Message Re-transmission

TODO

ocpp.awaiting_timeout = 30s

ocpp.retry_interval = 30s

Message Format Checking

TODO

#ocpp.message_format_checking = all

#ocpp.json_schema_dir = ${application_priv}/schemas

#ocpp.json_schema_id_prefix = urn:OCPP:1.6:2019:12:

Management and Observability

Manage Clients

Observe the messaging state