OCPP 2.0.1 Edition 4

Display Message Flows - CSMS Developer Guide

Based on OCPP 2.0.1 Edition 4 Specification (Part 2, Section O). This guide covers all display message flows from the CSMS (Charging Station Management System) perspective.

6 Sections

6 Use Cases

O01 - O06

1. Overview

Introduction

The DisplayMessage feature enables a CSO (via the CSMS) to display a message or a cycle of messages on a Charging Station, that is not part of the firmware of the Charging Station. The CSO gets full control over these messages: set, retrieve (get), replace, and clear.

Key Capabilities

Multi-Language Support

Messages can be configured in different languages. The Charging Station selects the correct language when displaying to a user.

Multiple Formats

Supports different formats (ASCII, HTML, URI, UTF8). See DisplayMessageSupportedFormats configuration variable.

Display Control

Each message has parameters to control when and how it is shown: priority, state, start/end time.

Full CRUD Operations

Complete lifecycle management: set (create), get (retrieve), replace (update), and clear (delete) messages on Charging Stations.

Important: It is NOT possible to retrieve/modify messages not configured via SetDisplayMessageRequest. Messages coded in the firmware of a Charging Station cannot be modified via OCPP.

OCPP Message Routing

All Display Message operations use the standard OCPP 2.0.1 JSON-RPC framing:

Frame Type	Format
`CALL`	`[2, "<messageId>", "<action>", {<payload>}]`
`CALLRESULT`	`[3, "<messageId>", {<payload>}]`
`CALLERROR`	`[4, "<messageId>", "<errorCode>", "<errorDescription>", {<errorDetails>}]`

Involved Messages

Message	Direction	Description
`SetDisplayMessageRequest`	CSMS -> CS	Set/replace a display message on a Charging Station
`SetDisplayMessageResponse`	CS -> CSMS	Response indicating acceptance/rejection
`GetDisplayMessagesRequest`	CSMS -> CS	Request stored display messages from a Charging Station
`GetDisplayMessagesResponse`	CS -> CSMS	Immediate acknowledgment (messages follow async)
`NotifyDisplayMessagesRequest`	CS -> CSMS	Async delivery of requested display messages
`NotifyDisplayMessagesResponse`	CSMS -> CS	Acknowledgment of received notification
`ClearDisplayMessageRequest`	CSMS -> CS	Remove a specific display message
`ClearDisplayMessageResponse`	CS -> CSMS	Response indicating if message was cleared

2. Shared Data Types

Reference

2.1 MessageInfoType

Central data type used in SetDisplayMessageRequest and NotifyDisplayMessagesRequest.

Field	Type	Required	Description
`id`	integer	Yes	Unique identifier for this message (positive integer >= 0). Assigned by the CSMS.
`priority`	MessagePriorityEnumType	Yes	Display priority of the message
`state`	MessageStateEnumType	No	During which Charging Station state to show. If omitted: show in any state.
`startDateTime`	dateTime (RFC 3339)	No	When to start showing. If omitted: immediately.
`endDateTime`	dateTime (RFC 3339)	No	When to stop showing. After this time, the CS SHALL remove the message.
`transactionId`	string (max 36)	No	If set, show only during this transaction. CS removes after transaction ends.
`message`	MessageContentType	Yes	The actual message content to display
`display`	ComponentType	No	Target display component (for stations with multiple displays)

2.2 MessageContentType

Field	Type	Required	Description
`format`	MessageFormatEnumType	Yes	Format of the message content
`language`	string (max 8)	No	Language code per RFC 5646 (e.g., "en", "nl", "de")
`content`	string (max 512)	Yes	The actual message text/content

2.3 MessageFormatEnumType

Value	Description
`ASCII`	Plain ASCII text
`HTML`	HTML formatted message
`URI`	URI pointing to message content
`UTF8`	UTF-8 encoded text

2.4 MessagePriorityEnumType

Value	Description
`AlwaysFront`	Message should always be shown on the front/main screen. Takes highest priority.
`InFront`	Show in front when the appropriate state is active (higher priority than NormalCycle)
`NormalCycle`	Show in the normal message rotation cycle

2.5 MessageStateEnumType

Value	Description
`Charging`	Show only when a transaction is active (charging)
`Faulted`	Show only when the Charging Station is in a faulted state
`Idle`	Show only when the Charging Station is idle (no transaction)
`Unavailable`	Show only when the Charging Station is unavailable

2.6 Response Status Enums

DisplayMessageStatusEnumType (SetDisplayMessage response)

Value	Description
`Accepted`	Message was accepted and will be displayed
`NotSupportedMessageFormat`	The message format is not supported by the CS
`Rejected`	Message was rejected (generic rejection)
`NotSupportedPriority`	The requested priority level is not supported
`NotSupportedState`	The requested state is not supported
`UnknownTransaction`	The referenced transactionId is unknown to the CS

GetDisplayMessagesStatusEnumType (GetDisplayMessages response)

Value	Description
`Accepted`	Request accepted, matching messages will be sent via NotifyDisplayMessagesRequest
`Unknown`	No messages matching the request criteria are known

ClearMessageStatusEnumType (ClearDisplayMessage response)

Value	Description
`Accepted`	Message was successfully removed
`Unknown`	The message id is not known on the Charging Station

2.7 ComponentType & EVSEType

Used for targeting a specific display on Charging Stations with multiple displays.

ComponentType

Field	Type	Required	Description
`name`	string (max 50)	Yes	Component name (case-insensitive, use CamelCase)
`instance`	string (max 50)	No	Instance name if component exists as multiple instances
`evse`	EVSEType	No	EVSE reference if display is EVSE-specific

EVSEType

Field	Type	Required	Description
`id`	integer	Yes	EVSE identifier (> 0)
`connectorId`	integer	No	Specific connector on the EVSE

2.8 StatusInfoType

Used in all responses to provide additional information about a status.

StatusInfoType Schema

{
  "reasonCode": "string (max 20)",               // REQUIRED, case-insensitive predefined code
  "additionalInfo": "string (max 512)"           // optional, detailed human-readable information
}

3. OCPP Messages

Protocol

3.1 SetDisplayMessageRequest (CSMS -> CS)

Action: "SetDisplayMessage"

CSMS --> Charging Station

Field	Type	Required	Description
`message`	MessageInfoType	Yes	The message to display

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "message": {
      "$ref": "#/definitions/MessageInfoType"
    }
  },
  "required": ["message"]
}

Example CALL

[2, "msg-001", "SetDisplayMessage", {
  "message": {
    "id": 1,
    "priority": "NormalCycle",
    "state": "Idle",
    "startDateTime": "2025-01-15T08:00:00Z",
    "endDateTime": "2025-01-31T23:59:59Z",
    "message": {
      "format": "UTF8",
      "language": "en",
      "content": "Welcome! Special rate today: $0.25/kWh"
    }
  }
}]

3.2 SetDisplayMessageResponse (CS -> CSMS)

Charging Station --> CSMS

Field	Type	Required	Description
`status`	DisplayMessageStatusEnumType	Yes	Whether the CS can display the message
`statusInfo`	StatusInfoType	No	Additional detail about the status

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "status": {
      "$ref": "#/definitions/DisplayMessageStatusEnumType"
    },
    "statusInfo": {
      "$ref": "#/definitions/StatusInfoType"
    }
  },
  "required": ["status"]
}

Example CALLRESULT

[3, "msg-001", {
  "status": "Accepted"
}]

3.3 GetDisplayMessagesRequest (CSMS -> CS)

Action: "GetDisplayMessages"

CSMS --> Charging Station

Field	Type	Required	Description
`requestId`	integer	Yes	Unique request ID for correlating async responses
`id`	array of integer	No	Filter: specific message IDs to retrieve. Must not exceed NumberOfDisplayMessages.maxLimit.
`priority`	MessagePriorityEnumType	No	Filter: only return messages with this priority
`state`	MessageStateEnumType	No	Filter: only return messages with this state

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "id": {
      "type": "array",
      "items": { "type": "integer" },
      "minItems": 1
    },
    "requestId": {
      "description": "The Id of this request.",
      "type": "integer"
    },
    "priority": {
      "$ref": "#/definitions/MessagePriorityEnumType"
    },
    "state": {
      "$ref": "#/definitions/MessageStateEnumType"
    }
  },
  "required": ["requestId"]
}

Example CALL (Get All)

[2, "msg-003", "GetDisplayMessages", {
  "requestId": 42
}]

3.4 GetDisplayMessagesResponse (CS -> CSMS)

Charging Station --> CSMS

Field	Type	Required	Description
`status`	GetDisplayMessagesStatusEnumType	Yes	Whether matching messages exist
`statusInfo`	StatusInfoType	No	Additional detail

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "status": {
      "$ref": "#/definitions/GetDisplayMessagesStatusEnumType"
    },
    "statusInfo": {
      "$ref": "#/definitions/StatusInfoType"
    }
  },
  "required": ["status"]
}

Example CALLRESULT

[3, "msg-003", {
  "status": "Accepted"
}]

3.5 NotifyDisplayMessagesRequest (CS -> CSMS)

Action: "NotifyDisplayMessages" - Async response to a previous GetDisplayMessagesRequest.

Charging Station --> CSMS

Field	Type	Required	Description
`requestId`	integer	Yes	The requestId from the original GetDisplayMessagesRequest
`messageInfo`	array of MessageInfoType	No	The display messages matching the request
`tbc`	boolean	No	"To be continued". true = more parts follow. Default: false.

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "messageInfo": {
      "type": "array",
      "items": {
        "$ref": "#/definitions/MessageInfoType"
      },
      "minItems": 1
    },
    "requestId": {
      "description": "The id of the GetDisplayMessagesRequest that requested this message.",
      "type": "integer"
    },
    "tbc": {
      "description": "to be continued indicator. Default value when omitted is false.",
      "type": "boolean",
      "default": false
    }
  },
  "required": ["requestId"]
}

Example CALL (from CS)

[2, "notify-001", "NotifyDisplayMessages", {
  "requestId": 42,
  "tbc": false,
  "messageInfo": [
    {
      "id": 1,
      "priority": "NormalCycle",
      "state": "Idle",
      "message": {
        "format": "UTF8",
        "language": "en",
        "content": "Welcome! Special rate: $0.25/kWh"
      }
    },
    {
      "id": 2,
      "priority": "InFront",
      "state": "Charging",
      "transactionId": "txn-abc-123",
      "message": {
        "format": "UTF8",
        "language": "en",
        "content": "Current cost: $3.50 | Energy: 14.2 kWh"
      }
    }
  ]
}]

3.6 NotifyDisplayMessagesResponse (CSMS -> CS)

CSMS --> Charging Station

The CSMS SHALL always respond with an empty NotifyDisplayMessagesResponse. No fields are defined (besides optional customData).

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    }
  }
}

Example CALLRESULT

[3, "notify-001", {}]

3.7 ClearDisplayMessageRequest (CSMS -> CS)

Action: "ClearDisplayMessage"

CSMS --> Charging Station

Field	Type	Required	Description
`id`	integer	Yes	The ID of the message to remove

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "id": {
      "description": "Id of the message that SHALL be removed from the Charging Station.",
      "type": "integer"
    }
  },
  "required": ["id"]
}

Example CALL

[2, "msg-008", "ClearDisplayMessage", {
  "id": 1
}]

3.8 ClearDisplayMessageResponse (CS -> CSMS)

Charging Station --> CSMS

Field	Type	Required	Description
`status`	ClearMessageStatusEnumType	Yes	Whether the message was cleared
`statusInfo`	StatusInfoType	No	Additional detail

JSON Schema

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "customData": {
      "$ref": "#/definitions/CustomDataType"
    },
    "status": {
      "$ref": "#/definitions/ClearMessageStatusEnumType"
    },
    "statusInfo": {
      "$ref": "#/definitions/StatusInfoType"
    }
  },
  "required": ["status"]
}

Example CALLRESULT

[3, "msg-008", {
  "status": "Accepted"
}]

4. Display Message Flows

Use Cases O01-O06

O01

Set DisplayMessage

The CSMS sends a message to a Charging Station to be displayed (e.g., promotional info, maintenance notice).

Prerequisite: The Charging Station supports the DisplayMessage feature.

Sequence Diagram:

Sequence Diagram

CSO                    CSMS                     Charging Station
 |                      |                            |
 |-- set a message ---->|                            |
 |                      |-- SetDisplayMessageReq --->|
 |                      |     (message)              |
 |                      |<-- SetDisplayMessageRes ---|
 |                      |     (status)               |
 |                      |                            |

CSMS Actions:

Receive trigger from CSO/operator to display a message on a specific Charging Station
Build a SetDisplayMessageRequest with a MessageInfoType payload
Send the request to the Charging Station via the WebSocket connection
Handle the SetDisplayMessageResponse

Response handling:

Status	Action
`Accepted`	Store the message ID in CSMS database for future reference (get/clear/replace)
`NotSupportedMessageFormat`	The format used is not supported; retry with a different format
`NotSupportedPriority`	The priority is not supported; retry with a different priority
`NotSupportedState`	The state filter is not supported; retry without state or different state
`UnknownTransaction`	The transactionId does not exist on the CS
`Rejected`	Generic rejection; log and inform operator

Requirements:

ID	Precondition	CSMS Requirement
`O01.FR.01`	CSMS wants to set a display message	CSMS SHALL send a SetDisplayMessageRequest with a MessageInfoType containing the message.
`O01.FR.02`	CS accepts the request	CS responds with SetDisplayMessageResponse with status Accepted.
`O01.FR.03`	CS does not support the message format	CS responds with status NotSupportedMessageFormat.
`O01.FR.04`	CS does not support the requested priority	CS responds with status NotSupportedPriority.
`O01.FR.05`	CS does not support the requested state	CS responds with status NotSupportedState.
`O01.FR.09`	Message has a startDateTime in the future	CS SHALL store the message and start showing it at the specified time.
`O01.FR.10`	Message has an endDateTime	CS SHALL stop showing and remove the message after the specified time.
`O01.FR.11`	CSMS sets a message with a display component	The message is targeted at a specific display on the CS.

Example - Set a promotional message

[2, "msg-001", "SetDisplayMessage", {
  "message": {
    "id": 1,
    "priority": "NormalCycle",
    "state": "Idle",
    "startDateTime": "2025-01-15T08:00:00Z",
    "endDateTime": "2025-01-31T23:59:59Z",
    "message": {
      "format": "UTF8",
      "language": "en",
      "content": "Welcome! Special rate today: $0.25/kWh"
    }
  }
}]

O02

Set DisplayMessage for Transaction

The CSMS sends a message to be displayed during a specific (ongoing) transaction. The message is automatically removed when the transaction ends.

Prerequisite: The Charging Station supports DisplayMessage and there is an ongoing transaction.

Sequence Diagram:

Sequence Diagram

CSO                    CSMS                     Charging Station
 |                      |                            |
 |-- set a message ---->|                            |
 |   for transaction    |                            |
 |                      |-- SetDisplayMessageReq --->|
 |                      |     (message+transId)      |
 |                      |<-- SetDisplayMessageRes ---|
 |                      |     (status)               |
 |                      |                            |

CSMS Actions:

Receive trigger to display a transaction-specific message (e.g., running cost info, charging status)
Build a SetDisplayMessageRequest with transactionId set in the MessageInfoType
Send the request to the Charging Station
Handle the response: Accepted = message shows during the transaction and auto-removes when it ends; UnknownTransaction = verify the transaction is still active; Other statuses = handle as in O01

Requirements:

ID	Precondition	CSMS Requirement
`O02.FR.01`	CSMS wants to set a message for a specific transaction	CSMS SHALL send a SetDisplayMessageRequest with transactionId in the MessageInfoType.
`O02.FR.02`	CS accepts the request	CS responds with Accepted. Message is shown during the transaction.
`O02.FR.03`	The referenced transactionId is unknown to the CS	CS responds with UnknownTransaction.
`O02.FR.07`	Transaction ends	CS SHALL automatically remove the message.

Example - Transaction-specific message

[2, "msg-002", "SetDisplayMessage", {
  "message": {
    "id": 2,
    "priority": "InFront",
    "state": "Charging",
    "transactionId": "txn-abc-123",
    "message": {
      "format": "UTF8",
      "language": "en",
      "content": "Current cost: $3.50 | Energy: 14.2 kWh"
    }
  }
}]

O03

Get All DisplayMessages

The CSMS requests all display messages currently configured on a Charging Station. The CS responds with an immediate acknowledgment, then asynchronously sends all messages.

Prerequisite: The Charging Station supports the DisplayMessage feature.

Sequence Diagram:

Sequence Diagram

CSO                    CSMS                     Charging Station
 |                      |                            |
 |-- get all messages ->|                            |
 |                      |-- GetDisplayMessagesReq -->|
 |                      |     (requestId)            |
 |                      |<-- GetDisplayMessagesRes --|
 |                      |     (status)               |
 |                      |                            |
 |                      |  [If status = Accepted]    |
 |                      |                            |
 |                      |  loop [for each part]      |
 |                      |<- NotifyDisplayMsgsReq ----|
 |                      |    (requestId, msgs, tbc)  |
 |                      |-- NotifyDisplayMsgsRes --->|
 |                      |                            |

CSMS Actions:

Generate a unique requestId (integer) to correlate the request with async responses
Send a GetDisplayMessagesRequest with only the requestId (no filters)
Handle the GetDisplayMessagesResponse: Accepted = messages will follow asynchronously; Unknown = no display messages are configured
Handle incoming NotifyDisplayMessagesRequest messages: match on requestId, check tbc flag (true = more follow, false/omitted = last batch), process the messageInfo array
Always respond with an empty NotifyDisplayMessagesResponse

Requirements:

ID	Precondition	CSMS Requirement
`O03.FR.01`	CSMS wants to retrieve all display messages	CSMS SHALL send a GetDisplayMessagesRequest with a requestId. No filters.
`O03.FR.02`	CS has matching display messages	CS responds with Accepted, then sends NotifyDisplayMessagesRequest with the messages.
`O03.FR.03`	CS has no display messages	CS responds with Unknown. No NotifyDisplayMessagesRequest will follow.
`O03.FR.04`	CSMS receives NotifyDisplayMessagesRequest	CSMS SHALL respond with an empty NotifyDisplayMessagesResponse.
`O03.FR.05`	tbc is true in NotifyDisplayMessagesRequest	CSMS should expect more NotifyDisplayMessagesRequest messages for this requestId.

Example - Get all messages

[2, "msg-003", "GetDisplayMessages", {
  "requestId": 42
}]

O04

Get Specific DisplayMessages

The CSMS requests specific display messages by ID, or filtered by priority/state. Same message flow as O03 but with filters applied.

Prerequisite: The Charging Station supports the DisplayMessage feature.

Same sequence as O03 but with filter parameters. The CSMS can filter by specific message IDs, priority level, or Charging Station state.

CSMS Actions:

Generate a unique requestId
Send a GetDisplayMessagesRequest with one or more filters: id (array of message IDs), priority (filter by priority level), state (filter by CS state)
Handle the GetDisplayMessagesResponse and subsequent NotifyDisplayMessagesRequest messages (same as O03)

Requirements:

ID	Precondition	CSMS Requirement
`O04.FR.01`	CSMS wants specific messages	CSMS SHALL send a GetDisplayMessagesRequest with requestId and filter(s): id, priority, and/or state.
`O04.FR.02`	CS has matching messages	CS responds with Accepted, then sends matching messages via NotifyDisplayMessagesRequest.
`O04.FR.03`	No messages match the filter criteria	CS responds with Unknown.
`O04.FR.04`	id array constraint	The id array SHALL NOT contain more ids than NumberOfDisplayMessages.maxLimit.

Example - Filter by specific IDs

[2, "msg-004", "GetDisplayMessages", {
  "requestId": 43,
  "id": [1, 3, 5]
}]

Example - Filter by priority

[2, "msg-005", "GetDisplayMessages", {
  "requestId": 44,
  "priority": "AlwaysFront"
}]

Example - Filter by state

[2, "msg-006", "GetDisplayMessages", {
  "requestId": 45,
  "state": "Idle"
}]

Example - Combined filters

[2, "msg-007", "GetDisplayMessages", {
  "requestId": 46,
  "priority": "NormalCycle",
  "state": "Charging"
}]

O05

Clear a DisplayMessage

The CSMS removes a specific display message from a Charging Station by its ID.

Prerequisite: The Charging Station supports the DisplayMessage feature.

Sequence Diagram:

Sequence Diagram

CSO                    CSMS                     Charging Station
 |                      |                            |
 |-- clear message ---->|                            |
 |                      |-- ClearDisplayMsgReq ----->|
 |                      |     (id)                   |
 |                      |<-- ClearDisplayMsgRes -----|
 |                      |     (status)               |
 |                      |                            |

CSMS Actions:

Identify the message ID to clear (from CSMS database or from a previous GetDisplayMessages result)
Send a ClearDisplayMessageRequest with the message id
Handle the ClearDisplayMessageResponse: Accepted = message was successfully removed, update CSMS database; Unknown = the message ID is not known on the CS (may have already been cleared or expired)

Requirements:

ID	Precondition	CSMS Requirement
`O05.FR.01`	CSMS wants to remove a display message	CSMS SHALL send a ClearDisplayMessageRequest with the message id.
`O05.FR.02`	CS has the message with the given id	CS responds with Accepted and removes the message.
`O05.FR.03`	CS does not have a message with the given id	CS responds with Unknown.

Example - Clear message

[2, "msg-008", "ClearDisplayMessage", {
  "id": 1
}]

O06

Replace DisplayMessage

The CSMS replaces an existing display message on a Charging Station by sending a new SetDisplayMessageRequest with the same message id.

Prerequisite: The Charging Station supports DisplayMessage and a message with the given id already exists.

Sequence Diagram:

Sequence Diagram

CSO                    CSMS                     Charging Station
 |                      |                            |
 |-- replace message -->|                            |
 |                      |-- SetDisplayMessageReq --->|
 |                      |     (message with          |
 |                      |      existing id)          |
 |                      |<-- SetDisplayMessageRes ---|
 |                      |     (status)               |
 |                      |                            |

CSMS Actions:

Identify the message to replace (using a known message id previously set)
Build a SetDisplayMessageRequest with the same id as the existing message, but with updated content/parameters
Send the request to the Charging Station
Handle the response (same as O01): Accepted = the existing message was replaced with the new content

Requirements:

ID	Precondition	CSMS Requirement
`O06.FR.01`	CSMS wants to replace an existing message	CSMS SHALL send a SetDisplayMessageRequest with the same id as the message to replace.
`O06.FR.02`	CS has the message with the given id	CS replaces the message and responds with Accepted.
`O06.FR.03`	CS does not have a message with the given id	CS treats it as a new message (same behavior as O01).

Example - Replace message id=1 with new content

[2, "msg-009", "SetDisplayMessage", {
  "message": {
    "id": 1,
    "priority": "NormalCycle",
    "state": "Idle",
    "startDateTime": "2025-02-01T00:00:00Z",
    "endDateTime": "2025-02-28T23:59:59Z",
    "message": {
      "format": "UTF8",
      "language": "en",
      "content": "February Special: Free charging on weekends!"
    }
  }
}]

5. Configuration Variables

Config

The CSMS should query these configuration variables (via GetVariables) to understand the Charging Station's DisplayMessage capabilities.

DisplayMessageCtrlr Configuration

Variable	Description
`DisplayMessageCtrlr.Available`	Whether the DisplayMessage feature is available
`DisplayMessageCtrlr.Enabled`	Whether the DisplayMessage feature is enabled
`NumberOfDisplayMessages`	Maximum number of display messages the CS can store. maxLimit constrains the id array in GetDisplayMessagesRequest.
`DisplayMessageSupportedFormats`	Comma-separated list of supported MessageFormatEnumType values (e.g., "ASCII,UTF8,HTML")
`DisplayMessageSupportedPriorities`	Comma-separated list of supported MessagePriorityEnumType values (e.g., "NormalCycle,InFront,AlwaysFront")

6. CSMS Implementation Checklist

Implementation

Database Schema Considerations

The CSMS should maintain a display_messages table to track messages sent to Charging Stations:

Column	Description
`id (integer)`	The message ID (unique per Charging Station)
`charge_point_id`	Reference to the Charging Station
`priority`	MessagePriorityEnumType value
`state`	Optional MessageStateEnumType value
`start_date_time`	Optional start time
`end_date_time`	Optional end time
`transaction_id`	Optional transaction reference
`message_format`	MessageFormatEnumType value
`message_language`	Optional language code
`message_content`	The message text (max 512 chars)
`display_component`	Optional target display
`status`	Current status (active, cleared, expired, etc.)
`created_at / updated_at`	Timestamps

Message Handlers to Implement

CSMS-Initiated (Outbound) Messages

Handler	Trigger	Action
`send_set_display_message`	Operator/API request	Build and send SetDisplayMessageRequest, handle response
`send_get_display_messages`	Operator/API request	Build and send GetDisplayMessagesRequest, track requestId
`send_clear_display_message`	Operator/API request	Build and send ClearDisplayMessageRequest, handle response

CS-Initiated (Inbound) Messages

Handler	Incoming Message	CSMS Action
`handle_notify_display_messages`	NotifyDisplayMessagesRequest	Match requestId, process messageInfo array, check tbc flag, respond with empty NotifyDisplayMessagesResponse

Error Handling

Timeout

If no SetDisplayMessageResponse / ClearDisplayMessageResponse / GetDisplayMessagesResponse is received within the configured message timeout, treat the operation as failed.

Partial NotifyDisplayMessages

If tbc=true is received but no subsequent NotifyDisplayMessagesRequest arrives, implement a reasonable timeout to consider the retrieval incomplete.

ID Management

The CSMS is responsible for assigning and tracking unique message IDs per Charging Station. IDs must be positive integers (>= 0).

Expired Messages

Messages with endDateTime in the past are automatically removed by the CS. The CSMS should also clean up its local database accordingly.

Transaction-bound Messages

Messages with transactionId are automatically removed by the CS when the transaction ends. The CSMS should track this and update its database.