DESCRIPTION

The coap_register_handler() function registers a callback handler handler that is called when there is a URI match against the resource and there is a method (e.g. PUT, POST etc.) match. method can be one of the following.

COAP_REQUEST_GET
COAP_REQUEST_POST
COAP_REQUEST_PUT
COAP_REQUEST_DELETE
COAP_REQUEST_FETCH
COAP_REQUEST_PATCH
COAP_REQUEST_IPATCH

The handler function prototype is defined as:

typedef void (*coap_method_handler_t)(coap_context_t *context,
                                      coap_resource_t *resource,
                                      coap_session_t *session,
                                      coap_pdu_t *incoming_pdu,
                                      coap_string_t *token,
                                      coap_string_t *query,
                                      coap_pdu_t *response_pdu);

The coap_register_response_handler() function defines a request’s response handler for traffic associated with the context. The application can use this for handling any response packets, including sending a RST packet if this response was unexpected. If handler is NULL, then the handler is de-registered.

The handler function prototype is defined as:

typedef void (*coap_response_handler_t)(coap_context_t *context,
                                        coap_session_t *session,
                                        coap_pdu_t *sent,
                                        coap_pdu_t *received,
                                        const coap_tid_t id);

The coap_register_nack_handler() function defines a request’s negative response handler for traffic associated with the context. If handler is NULL, then the handler is de-registered.

The handler function prototype is defined as:

typedef void (*coap_nack_handler_t)(coap_context_t *context,
                                    coap_session_t *session,
                                    coap_pdu_t *sent,
                                    coap_nack_reason_t reason,
                                    const coap_tid_t id);

The coap_register_ping_handler() function defines a handler for tracking CoAP ping traffic associated with the context. If handler is NULL, then the handler is de-registered.

The handler function prototype is defined as:

typedef void (*coap_ping_handler_t)(coap_context_t *context,
                                    coap_session_t *session,
                                    coap_pdu_t *received,
                                    const coap_tid_t id);

The coap_register_pong_handler() function defines a handler for tracking CoAP TCP ping response traffic associated with the context. If handler is NULL, then the handler is de-registered.

The handler function prototype is defined as:

typedef void (*coap_pong_handler_t)(coap_context_t *context,
                                    coap_session_t *session,
                                    coap_pdu_t *received,
                                    const coap_tid_t id);

The coap_register_event_handler() function defines a handler for tracking (D)TLS events associated with the context. If handler is NULL, then the handler is de-registered.

The handler function prototype is defined as:

typedef void (*coap_event_handler_t)(coap_context_t *context,
                                     coap_event_t event,
                                     coap_session_t *session);

Events can be one of the following

/**
 * (D)TLS events for COAP_PROTO_DTLS and COAP_PROTO_TLS
 */
COAP_EVENT_DTLS_CLOSED        0x0000
COAP_EVENT_DTLS_CONNECTED     0x01DE
COAP_EVENT_DTLS_RENEGOTIATE   0x01DF
COAP_EVENT_DTLS_ERROR         0x0200
/**
 * TCP events for COAP_PROTO_TCP and COAP_PROTO_TLS
 */
COAP_EVENT_TCP_CONNECTED      0x1001
COAP_EVENT_TCP_CLOSED         0x1002
COAP_EVENT_TCP_FAILED         0x1003
/**
 * CSM exchange events for reliable protocols only
 */
COAP_EVENT_SESSION_CONNECTED  0x2001
COAP_EVENT_SESSION_CLOSED     0x2002
COAP_EVENT_SESSION_FAILED     0x2003

EXAMPLES

GET Resource Callback Handler

#include <coap2/coap.h>

void
hnd_get_time(coap_context_t *context, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {

  unsigned char buf[40];
  size_t len;
  time_t now;

  /* ... Additional analysis code for resource, request pdu etc.  ... */

  /* After analysis, generate a suitable response */

  /* Note that token, if set, is already in the response pdu */

  now = time(NULL);

  if (query != NULL && coap_string_equal(query, coap_make_str_const("secs"))) {
    /* Output secs since Jan 1 1970 */
    len = snprintf((char *)buf, sizeof(buf), "%lu", now);
  }
  else {
    /* Output human-readable time */
    struct tm *tmp;
    tmp = gmtime(&now);
    if (!tmp) {
      /* If 'now' is not valid */
      response->code = COAP_RESPONSE_CODE(404);
      return;
    }
    len = strftime((char *)buf, sizeof(buf), "%b %d %H:%M:%S", tmp);
  }
  /*
   * Invoke coap_add_data_blocked_response() to do all the hard work.
   *
   * Define the format - COAP_MEDIATYPE_TEXT_PLAIN - to add in
   * Define how long this response is valid for (secs) - 1 - to add in.
   *
   * OBSERVE Option added internally if needed within the function
   * BLOCK2 Option added internally if output too large
   * ETAG Option added internally
   */
  coap_add_data_blocked_response(resource, session, request, response, token,
                                 COAP_MEDIATYPE_TEXT_PLAIN, 1,
                                 len,
                                 buf);

  /*
   * As resource->code has been updated in coap_add_data_blocked_response(),
   * the response pdu will be transmitted by the underlying library.
   */

}

Packet Response Handler

#include <coap2/coap.h>

static void
response_handler(coap_context_t *ctx, coap_session_t *session,
coap_pdu_t *sent, coap_pdu_t *received, const coap_tid_t id) {

  coap_pdu_t *pdu = NULL;
  coap_opt_t *block_opt;
  coap_opt_iterator_t opt_iter;
  unsigned char buf[4];
  size_t len;
  unsigned char *databuf;
  coap_tid_t tid;

  /* check if this is a response to our original request */
  if (!check_token(received)) {
    /* drop if this was just some message, or send RST in case of notification */
    if (!sent && (received->type == COAP_MESSAGE_CON ||
                  received->type == COAP_MESSAGE_NON))
      coap_send_rst(session, received);
    return;
  }

  if (received->type == COAP_MESSAGE_RST) {
    info("got RST\n");
    return;
  }

  /* Output the received data, if any */
  if (COAP_RESPONSE_CLASS(received->code) == 2) {
    /* Additional code to deal with the response */

  }
  return;

}

SEE ALSO

coap_resource(3)

FURTHER INFORMATION

See "RFC7252: The Constrained Application Protocol (CoAP)" for further information.

BUGS

Please report bugs on the mailing list for libcoap: libcoap-developers@lists.sourceforge.net

AUTHORS

The libcoap project <libcoap-developers@lists.sourceforge.net>