ocpp - v0.4.0

ocpp/transport/json/frame

OCPP-J wire framing.

On the JSON/WebSocket transport every message is a JSON array:

CALL [2, messageId, action, payload] CALLRESULT [3, messageId, payload] CALLERROR [4, messageId, errorCode, errorDescription, errorDetails] CALLRESULTERROR [5, messageId, errorCode, errorDescription, errorDetails] (2.1+) SEND [6, messageId, action, payload] (2.1+)

CallResultError and Send are OCPP 2.1 additions: version policy (a 1.6/2.0.1 peer must never emit them) belongs to the caller, not this grammar — the decoder accepts all five on every connection. Per part 4 §4.1.3 a receiver SHALL ignore a frame with an unrecognized message type — the entire message, as clarified by the 2026-04 erratum [1163], which also removed the old §4.4 fallback of answering it with a MessageTypeNotSupported CALLERROR — so UnknownMessageType is best treated as ignorable, not fatal.

Decoded payloads are kept as raw Dynamic so the caller can run the appropriate version- and action-specific payload decoder (see the per-version dispatch modules).

Types

Frame

</> 
pub type Frame {
  Call(id: String, action: String, payload: dynamic.Dynamic)
  CallResult(id: String, payload: dynamic.Dynamic)
  CallError(
    id: String,
    code: String,
    description: String,
    details: dynamic.Dynamic,
  )
  CallResultError(
    id: String,
    code: String,
    description: String,
    details: dynamic.Dynamic,
  )
  Send(id: String, action: String, payload: dynamic.Dynamic)
}

Constructors 

  • Call(id: String, action: String, payload: dynamic.Dynamic)
  • CallResult(id: String, payload: dynamic.Dynamic)
  • CallError(
  id: String,
  code: String,
  description: String,
  details: dynamic.Dynamic,
)
  • CallResultError(
  id: String,
  code: String,
  description: String,
  details: dynamic.Dynamic,
)

    (2.1) Error response to a CALLRESULT the caller could not process; id equals the id of the CALL/CALLRESULT exchange it refers to.

  • Send(id: String, action: String, payload: dynamic.Dynamic)

    (2.1) Unconfirmed message: no response may be sent, and it is exempt from the one-CALL-in-flight rule (e.g. NotifyPeriodicEventStream).

FrameError

</> 
pub type FrameError {
  MalformedJson(json.DecodeError)
  UnknownMessageType(Int)
}

Constructors

Values

decode

</> 
pub fn decode(input: String) -> Result(Frame, FrameError)

Parse an OCPP-J wire frame from its JSON string.

encode_call

</> 
pub fn encode_call(
  id: String,
  action: String,
  payload: json.Json,
) -> json.Json

encode_call_error

</> 
pub fn encode_call_error(
  id: String,
  code: rpc.ErrorCode,
  description: String,
  details: json.Json,
) -> json.Json

encode_call_result

</> 
pub fn encode_call_result(
  id: String,
  payload: json.Json,
) -> json.Json

encode_call_result_error

</> 
pub fn encode_call_result_error(
  id: String,
  code: rpc.ErrorCode,
  description: String,
  details: json.Json,
) -> json.Json

(2.1) Encode a CALLRESULTERROR: reports that the CALLRESULT received for id could not be processed.

encode_send

</> 
pub fn encode_send(
  id: String,
  action: String,
  payload: json.Json,
) -> json.Json

(2.1) Encode a SEND: an unconfirmed call-shaped message that expects no response.

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