Provided by: libcoap3_4.3.0-2build1_amd64 
NAME
coap_resource, coap_resource_init, coap_resource_unknown_init, coap_resource_proxy_uri_init,
coap_add_resource, coap_delete_resource, coap_resource_set_mode, coap_resource_set_userdata,
coap_resource_get_userdata - Work with CoAP resources
SYNOPSIS
#include <coap3/coap.h>
coap_resource_t *coap_resource_init(coap_str_const_t *uri_path, int flags);
coap_resource_t *coap_resource_unknown_init(coap_method_handler_t put_handler);
coap_resource_t *coap_resource_proxy_uri_init(coap_method_handler_t proxy_handler, size_t
host_name_count, const char *host_name_list[]);
void coap_add_resource(coap_context_t *context, coap_resource_t *resource);
int coap_delete_resource(coap_context_t *context, coap_resource_t *resource);
void coap_resource_set_mode(coap_resource_t *resource, int mode);
void coap_resource_set_userdata(coap_resource_t *resource, void *data);
void *coap_resource_get_userdata(coap_resource_t *resource);
void coap_resource_release_userdata_handler(coap_context_t *context,
coap_resource_release_userdata_handler_t callback);
coap_str_const_t *coap_resource_get_uri_path(coap_resource_t *resource);
For specific (D)TLS library support, link with -lcoap-3-notls, -lcoap-3-gnutls, -lcoap-3-openssl,
-lcoap-3-mbedtls or -lcoap-3-tinydtls. Otherwise, link with -lcoap-3 to get the default (D)TLS library
support.
DESCRIPTION
CoAP Resources on a CoAP Server need to be created and updated etc. The URI in the request packet defines
the resource to work with, with possibly the Query referring to a sub-resource.
When resources are configured on the CoAP server, the URI to match against in the request packet is
specified.
Callback Handlers are then added to the resource to handle the different request methods.
Adding Attributes allows textual information to be added to the resource which can then be reported back
to any client doing a "GET .well-known/core" request.
If an incoming packet request matches a resource’s URI and Method, then the appropriate callback resource
handler is invoked to process the packet which then should update a suitable response packet for sending
back to the requester.
There is support for handling incoming packets where the URI is unknown. This could, for example, happen
when a PUT request is trying to create a new resource. It is the responsibility of the unknown resource
callback handler to either create a new resource for the URI or just manage things separately.
CoAP Observe (RFC 7641) is not supported for unknown resources, so a new resource with GET handler must
be created by the unknown resource callback handle matching the URI which then can be Observable.
The coap_resource_init() function returns a newly created resource of type coap_resource_t * . uri_path
specifies the uri string path to match against. flags is used to define whether the resource is of type
Confirmable Message or Non-Confirmable Message for any "observe" responses. See coap_observe(3). flags
can be one of the following definitions or’ed together.
COAP_RESOURCE_FLAGS_NOTIFY_NON Set the notification message type to
non-confirmable for any trigggered
"observe" responses with type set to
confirmable every 5 packets as
required by RFC7641 section-4.5.
COAP_RESOURCE_FLAGS_NOTIFY_NON_ALWAYS Set the notification message type to
always non-confirmable for any
trigggered "observe" responses. This
should only be used if a upper layer
protocol requires it.
COAP_RESOURCE_FLAGS_NOTIFY_CON Set the notification message type to
confirmable for any trigggered
"observe" responses.
COAP_RESOURCE_FLAGS_RELEASE_URI Free off the coap_str_const_t for
uri_path when the resource is
deleted.
NOTE: uri_path, if not 7 bit readable ASCII, binary bytes must be hex encoded according to the rules
defined in RFC3968 Section 2.1.
The coap_resource_unknown_init() function returns a newly created resource of type coap_resource_t *.
put_handler is automatically added to the resource to handle PUT requests to resources that are unknown.
Additional handlers can be added to this resource if required.
The coap_resource_proxy_uri_init() function returns a newly created resource of type coap_resource_t *.
proxy_handler is automatically added to the resource to handle PUT/POST/GET etc. requests that use the
Proxy-Uri: option. There is no need to add explicit request type handlers. One or more names by which the
proxy is known by (IP address, DNS name etc.) must be supplied in the array defined by host_name_list[]
which has a count of host_name_count. This is used to check whether the current endpoint is the proxy
target address.
The coap_add_resource() function registers the given resource with the context. The resource must have
been created by coap_resource_init(), coap_resource_unknown_init() or coap_resource_proxy_uri_init(). The
storage allocated for the resource will be released by coap_delete_resource().
As the uri_path of the resource has to be unique across all of the resources associated with a context,
coap_add_resource() (or coap_add_resource_release()) will delete any previous resource with the same
uri_path before adding in the new resource.
The coap_delete_resource() function deletes a resource identified by resource from context. The storage
allocated for that resource is freed, along with any attrigutes associated with the resource.
The coap_resource_set_mode() changes the notification message type of resource to the given mode which
must be one of COAP_RESOURCE_FLAGS_NOTIFY_NON, COAP_RESOURCE_FLAGS_NOTIFY_NON_ALWAYS or
COAP_RESOURCE_FLAGS_NOTIFY_CON.
The coap_resource_set_userdata() function allows a pointer to user data to be associated with a resource
that can accessed in any callback that includes resource as a parameter.
NOTE: data must point to a static, or allocated, block of memory.
The coap_resource_get_userdata() function obtains the user data pointer from the resource that had
previously been set up by coap_resource_set_userdata().
The coap_resource_release_userdata_handler() function defines the context wide callback handler to call
to release the allocated user data that has been added to the resource using coap_resource_set_userdata()
when the resource is deleted. callback can be NULL (which is the default) if nothing needs to be freed
off.
The coap_resource_get_uri_path() function is used to obtain the UriPath of the resource definion.
RETURN VALUES
The coap_resource_init(), coap_resource_unknown_init() and coap_resource_proxy_uri_init() functions
return a newly created resource or NULL if there is a malloc failure.
The coap_delete_resource() function return 0 on failure (resource not found), 1 on success.
The coap_resource_get_userdata() function returns the value previously set by the
coap_resource_set_userdata() function or NULL.
The coap_resource_get_uri_path() function returns the uri_path or NULL if there was a failure.
EXAMPLES
Fixed Resources Set Up
#include <coap3/coap.h>
#define INDEX "This is an example server using libcoap\n"
static void
hnd_get_index(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
unsigned char buf[3];
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)request;
(void)query;
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTENT);
coap_add_option(response,
COAP_OPTION_CONTENT_TYPE,
coap_encode_var_safe(buf, sizeof(buf),
COAP_MEDIATYPE_TEXT_PLAIN),
buf);
coap_add_option(response,
COAP_OPTION_MAXAGE,
coap_encode_var_safe(buf, sizeof(buf), 0x2ffff), buf);
coap_add_data(response, strlen(INDEX), (const uint8_t *)INDEX);
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTENT);
}
static void
hnd_delete_time(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)request;
(void)query;
/* .. code .. */
coap_pdu_set_code(response, COAP_RESPONSE_CODE_DELETED);
}
static void
hnd_get_time(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)request;
(void)query;
(void)response;
/* .. code .. */
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTENT);
}
static void
hnd_put_time(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)request;
(void)query;
(void)response;
/* .. code .. */
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CHANGED);
}
static void
init_resources(coap_context_t *ctx) {
coap_resource_t *r;
/* Create a resource to return general information */
r = coap_resource_init(NULL, 0);
coap_register_handler(r, COAP_REQUEST_GET, hnd_get_index);
/* Document resource for '.well-known/core' request */
coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
coap_add_attr(r, coap_make_str_const("title"),
coap_make_str_const("\"General Info\""), 0);
coap_add_resource(ctx, r);
/* Create a resource to return return or update time */
r = coap_resource_init(coap_make_str_const("time"),
COAP_RESOURCE_FLAGS_NOTIFY_CON);
coap_resource_set_get_observable(r, 1);
coap_register_handler(r, COAP_REQUEST_GET, hnd_get_time);
coap_register_handler(r, COAP_REQUEST_PUT, hnd_put_time);
coap_register_handler(r, COAP_REQUEST_DELETE, hnd_delete_time);
/* Document resource for 'time' request */
coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
coap_add_attr(r, coap_make_str_const("title"),
coap_make_str_const("\"Internal Clock\""), 0);
coap_add_attr(r, coap_make_str_const("rt"), coap_make_str_const("\"secs\""),
0);
coap_add_attr(r, coap_make_str_const("if"), coap_make_str_const("\"clock\""),
0);
coap_add_resource(ctx, r);
}
Dynamic Resources Set Up
#include <coap3/coap.h>
/* Regular DELETE handler - used by resources created by the
* Unknown Resource PUT handler */
static void
hnd_delete(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)session;
(void)request;
(void)query;
(void)response;
/* .. code .. */
/* Dynamic resource no longer required - delete it */
coap_delete_resource(coap_session_get_context(session), resource);
coap_pdu_set_code(response, COAP_RESPONSE_CODE_DELETED);
}
/* Regular GET handler - used by resources created by the
* Unknown Resource PUT handler */
static void
hnd_get(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
coap_str_const_t *get_uri_path;
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)request;
(void)query;
(void)response;
/*
* request will be NULL if an Observe triggered request, so the uri_path,
* if needed, must be abstracted from the resource.
* The uri_path string is a const pointer
*/
get_uri_path = coap_resource_get_uri_path(resource);
/* .. code .. */
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTENT);
}
/* Regular PUT handler - used by resources created by the
* Unknown Resource PUT handler */
static void
hnd_put(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)resource;
(void)session;
(void)query;
coap_string_t *put_uri_path;
size_t length;
const uint8_t *data;
size_t offset;
size_t total;
int new_resource = 0;
/* get the uri_path */
put_uri_path = coap_get_uri_path(request);
if (!put_uri_path) {
coap_pdu_set_code(response, COAP_RESPONSE_CODE_NOT_FOUND);
return;
}
coap_get_data_large(request, &length, &data, &offset, &total);
/* .. code .. */
/* Need to do this as coap_get_uri_path() created it */
coap_delete_string(put_uri_path);
if (length + offset < total)
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTINUE);
else if (new_resource)
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CREATED);
else
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CHANGED);
}
static int
check_url_fn(coap_string_t *uri_path, uint8_t code) {
/* Remove (void) definition if variable is used */
(void)uri_path;
(void)code;
/* Code to determine whether the uri is valid or not */
return 1;
}
/* Unknown Resource PUT handler */
static void
hnd_unknown_put(coap_resource_t *resource, coap_session_t *session,
const coap_pdu_t *request, const coap_string_t *query, coap_pdu_t *response) {
/* Remove (void) definition if variable is used */
(void)resource;
coap_pdu_code_t req_code = coap_pdu_get_code(request);
coap_resource_t *r;
coap_string_t *uri_path;
/* get the uri_path - which will get used by coap_resource_init() */
uri_path = coap_get_uri_path(request);
if (!uri_path) {
coap_pdu_set_code(response, COAP_RESPONSE_CODE_NOT_FOUND);
return;
}
/* Check if new URI Path is valid */
if (!check_url_fn (uri_path, req_code)) {
coap_pdu_set_code(response, COAP_RESPONSE_CODE_NOT_FOUND);
coap_delete_string(uri_path);
return;
}
/*
* Create a resource to handle the new URI
* uri_path will get deleted when the resource is removed
*/
r = coap_resource_init((coap_str_const_t*)uri_path,
COAP_RESOURCE_FLAGS_RELEASE_URI | COAP_RESOURCE_FLAGS_NOTIFY_NON);
coap_register_handler(r, COAP_REQUEST_PUT, hnd_put);
coap_register_handler(r, COAP_REQUEST_DELETE, hnd_delete);
/* We possibly want to Observe the GETs */
coap_resource_set_get_observable(r, 1);
coap_register_handler(r, COAP_REQUEST_GET, hnd_get);
coap_add_resource(coap_session_get_context(session), r);
/* Do the PUT for this first call */
hnd_put(r, session, request, query, response);
return;
}
/* Initialize single Unknown Resource PUT handler */
static void
init_resources(coap_context_t *ctx) {
coap_resource_t *r;
/* Create a resource to handle PUTs to unknown URIs */
r = coap_resource_unknown_init(hnd_unknown_put);
/*
* Additional handlers can be added - for example
* coap_register_handler(r, COAP_REQUEST_POST, hnd_post_unknown);
* coap_register_handler(r, COAP_REQUEST_GET, hnd_get_unknown);
* coap_register_handler(r, COAP_REQUEST_DELETE, hnd_delete_unknown);
*/
coap_add_resource(ctx, r);
}
SEE ALSO
coap_attribute(3), coap_context(3), coap_observe(3) and coap_handler(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 or raise an
issue on GitHub at https://github.com/obgm/libcoap/issues
AUTHORS
The libcoap project <libcoap-developers@lists.sourceforge.net>