| COAP_HANDLER(3) | libcoap Manual | COAP_HANDLER(3) |
coap_handler, coap_register_handler, coap_register_response_handler, coap_register_nack_handler, coap_register_ping_handler, coap_register_pong_handler, coap_register_event_handler - work with CoAP handlers
#include <coap2/coap.h>
void coap_register_handler(coap_resource_t *resource, unsigned char method, coap_method_handler_t handler);
void coap_register_response_handler(coap_context_t *context, coap_response_handler_t handler);
void coap_register_nack_handler(coap_context_t *context, coap_nack_handler_t handler);
void coap_register_ping_handler(coap_context_t *context, coap_ping_handler_t handler);
void coap_register_pong_handler(coap_context_t *context, coap_pong_handler_t handler);
void coap_register_event_handler(coap_context_t *context, coap_event_handler_t handler);
Link with -lcoap-2, -lcoap-2-gnutls, -lcoap-2-openssl or -lcoap-2-tinydtls depending on your (D)TLS library type.
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
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 "RFC7252: The Constrained Application Protocol (CoAP)" for further information.
Please report bugs on the mailing list for libcoap: libcoap-developers@lists.sourceforge.net
The libcoap project <libcoap-developers@lists.sourceforge.net>
| 04/13/2019 | coap_handler 4.2.0 |