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CoAP Client

Simplified, event-driven CoAP client wrapper for ESP-IDF.

This module provides a high-level CoAP client with an API modeled after esp_mqtt_client . It wraps libcoap into a simple init/start/request/stop lifecycle with an internal request queue and unified event callback.

Type Definitions​

wb_coap_client_handle_t​

typedef struct wb_coap_client* wb_coap_client_handle_t

Opaque client handle.

wb_coap_event_handler_t​

typedef void(* wb_coap_event_handler_t) (wb_coap_event_data_t *event_data, void *user_ctx)

User event handler callback type.

Enumerations​

wb_coap_content_format_t​

CoAP content format identifiers.

EnumeratorValueDescription
WB_COAP_FORMAT_TEXT_PLAIN= 0
WB_COAP_FORMAT_LINK_FORMAT= 40
WB_COAP_FORMAT_XML= 41
WB_COAP_FORMAT_OCTET_STREAM= 42
WB_COAP_FORMAT_JSON= 50
WB_COAP_FORMAT_CBOR= 60

wb_coap_event_t​

CoAP event types delivered to the user callback.

EnumeratorValueDescription
WB_COAP_EVENT_CONNECTEDCoAP/DTLS session established.
WB_COAP_EVENT_DISCONNECTEDSession lost or closed.
WB_COAP_EVENT_RESPONSEResponse or Observe notification received.
WB_COAP_EVENT_ERRORInternal error occurred.

wb_coap_method_t​

CoAP request method enumeration.

EnumeratorValueDescription
WB_COAP_METHOD_GET= 1
WB_COAP_METHOD_POST= 2
WB_COAP_METHOD_PUT= 3
WB_COAP_METHOD_DELETE= 4

wb_coap_response_code_t​

CoAP response codes.

EnumeratorValueDescription
WB_COAP_RESP_CREATED= 0x41
WB_COAP_RESP_DELETED= 0x42
WB_COAP_RESP_VALID= 0x43
WB_COAP_RESP_CHANGED= 0x44
WB_COAP_RESP_CONTENT= 0x45
WB_COAP_RESP_BAD_REQUEST= 0x80
WB_COAP_RESP_UNAUTHORIZED= 0x81
WB_COAP_RESP_FORBIDDEN= 0x83
WB_COAP_RESP_NOT_FOUND= 0x84
WB_COAP_RESP_INTERNAL_SERVER_ERROR= 0xA0

wb_coap_security_t​

DTLS security mode selection.

EnumeratorValueDescription
WB_COAP_SECURITY_NONEPlain CoAP over UDP (no encryption)
WB_COAP_SECURITY_PSKDTLS with Pre-Shared Key.
WB_COAP_SECURITY_PKIDTLS with X.509 certificates.

Macros​

WB_COAP_CONNECTED_BIT BIT0​

Set when session is established.

WB_COAP_FAIL_BIT BIT1​

Set when connection attempt fails.

WB_COAP_LOCATION_MAX 128​

Maximum length for assembled Location-Path string.

WB_COAP_TOKEN_MAX_LEN 8​

Maximum CoAP token length per RFC 7252 (up to 8 bytes)

Functions​

wb_coap_client_delete​

Send a DELETE request.

esp_err_t wb_coap_client_delete(wb_coap_client_handle_t client, const char *path)

Parameters:

  • client (wb_coap_client_handle_t): Client handle
  • path (const char *): URI path

Returns:

ESP_OK if the request was queued

wb_coap_client_destroy​

Destroy the CoAP client and free all resources.

esp_err_t wb_coap_client_destroy(wb_coap_client_handle_t client)

Parameters:

  • client (wb_coap_client_handle_t): Client handle

Returns:

ESP_OK on success

wb_coap_client_get​

Send a GET request.

esp_err_t wb_coap_client_get(wb_coap_client_handle_t client, const char *path)

Parameters:

  • client (wb_coap_client_handle_t): Client handle
  • path (const char *): URI path, e.g. "/sensor/temperature"

Returns:

ESP_OK if the request was queued

wb_coap_client_init​

Initialize the CoAP client.

wb_coap_client_handle_t wb_coap_client_init(const wb_coap_client_config_t *config)

Parameters:

  • config (const wb_coap_client_config_t *): Pointer to client configuration

Returns:

Client handle on success, NULL on failure

Creates internal resources and the CoAP processing task.

wb_coap_client_is_connected​

Check whether the CoAP session is currently active.

bool wb_coap_client_is_connected(wb_coap_client_handle_t client)

Parameters:

  • client (wb_coap_client_handle_t): Client handle

Returns:

true if connected

wb_coap_client_observe​

Register an observe on a resource (GET with Observe option)

esp_err_t wb_coap_client_observe(wb_coap_client_handle_t client, const char *path)

Parameters:

  • client (wb_coap_client_handle_t): Client handle
  • path (const char *): URI path to observe

Returns:

ESP_OK if the observe request was queued

The server will send notifications whenever the resource changes. Notifications arrive via the event handler as WB_COAP_EVENT_RESPONSE.

wb_coap_client_post​

Send a POST request with payload.

esp_err_t wb_coap_client_post(wb_coap_client_handle_t client, const char *path, const uint8_t *data, size_t data_len, wb_coap_content_format_t format)

Parameters:

  • client (wb_coap_client_handle_t): Client handle
  • path (const char *): URI path
  • data (const uint8_t *): Payload data
  • data_len (size_t): Payload length
  • format (wb_coap_content_format_t): Content format

Returns:

ESP_OK if the request was queued

wb_coap_client_put​

Send a PUT request with payload.

esp_err_t wb_coap_client_put(wb_coap_client_handle_t client, const char *path, const uint8_t *data, size_t data_len, wb_coap_content_format_t format)

Parameters:

  • client (wb_coap_client_handle_t): Client handle
  • path (const char *): URI path
  • data (const uint8_t *): Payload data
  • data_len (size_t): Payload length
  • format (wb_coap_content_format_t): Content format

Returns:

ESP_OK if the request was queued

wb_coap_client_start​

Start / connect the CoAP client.

esp_err_t wb_coap_client_start(wb_coap_client_handle_t client)

Parameters:

  • client (wb_coap_client_handle_t): Client handle

Returns:

ESP_OK on success

Resolves the server address and establishes a CoAP session.

wb_coap_client_stop​

Stop the CoAP client.

esp_err_t wb_coap_client_stop(wb_coap_client_handle_t client)

Parameters:

  • client (wb_coap_client_handle_t): Client handle

Returns:

ESP_OK on success

Tears down the CoAP session but keeps resources allocated.