Provided by: libcoap3t64_4.3.4-1.1build4_amd64 
NAME
coap_resource, coap_resource_init, coap_resource_unknown_init, coap_resource_unknown_init2,
coap_resource_proxy_uri_init, coap_resource_proxy_uri_init2, coap_add_resource, coap_delete_resource,
coap_resource_set_mode, coap_resource_set_userdata, coap_resource_get_userdata,
coap_resource_release_userdata_handler, coap_resource_get_uri_path - 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_unknown_init2(coap_method_handler_t put_handler, int flags);
coap_resource_t *coap_resource_proxy_uri_init(coap_method_handler_t proxy_handler, size_t
host_name_count, const char *host_name_list[]);
coap_resource_t *coap_resource_proxy_uri_init2(coap_method_handler_t proxy_handler, size_t
host_name_count, const char *host_name_list[], int flags);
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, updated and deleted as appropriate. The URI in the
request packet defines the resource to work with, with possibly the Query or data in the request
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. See
coap_register_request_handler(3) for further information.
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. See coap_add_attr(3) for further information.
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 should then update a suitable response packet for
returning back to the requester.
There is support for handling incoming packets where the URI is unknown (no specific resource has been
created). 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 (RFC7641) 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.
There is support for handling incoming proxy based requests using the Proxy-Uri or Proxy-Scheme options.
FUNCTIONS
Function: coap_resource_init()
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. Normally there is no need for the leading / - e.g. just
"full/path/for/resource". flags can be zero or more 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 4.5.
Transmission". See coap_observe(3).
NOTE: This flag is ignored if
COAP_RESOURCE_FLAGS_NOTIFY_CON is
set.
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. See
coap_observe(3). NOTE: This flag is
ignored if
COAP_RESOURCE_FLAGS_NOTIFY_CON is
set.
COAP_RESOURCE_FLAGS_NOTIFY_CON Set the notification message type to
confirmable for any trigggered
"observe" responses. See
coap_observe(3). NOTE:
COAP_RESOURCE_FLAGS_NOTIFY_NON is
assumed if
COAP_RESOURCE_FLAGS_NOTIFY_CON is not
set.
COAP_RESOURCE_FLAGS_RELEASE_URI Free off the coap_str_const_t for
uri_path when the resource is
deleted.
COAP_RESOURCE_FLAGS_FORCE_SINGLE_BODY Force all large traffic to this
resource to be presented as a single
body to the request handler.
COAP_RESOURCE_FLAGS_OSCORE_ONLY Define this resource as an OSCORE
enabled access only.
NOTE: The following flags are only tested against if coap_mcast_per_resource() has been called. If
coap_mcast_per_resource() has not been called, then all resources have multicast support, libcoap adds in
random delays to the responses, and 4.xx / 5.xx responses are dropped.
NOTE: The pseudo resource for ".well-known/core" always has multicast support enabled and is not
configurable.
COAP_RESOURCE_FLAGS_HAS_MCAST_SUPPORT This resource has support for
multicast requests.
COAP_RESOURCE_FLAGS_LIB_DIS_MCAST_DELAYS Disable libcoap library from adding
in delays to multicast requests
before sending the response back to
the client. It is then the
responsibility of the app to delay
the responses for multicast requests.
See "RFC7252 8.2. Request/Response
Layer". However, the pseudo resource
for ".well-known/core" always has
multicast support enabled.
COAP_RESOURCE_FLAGS_LIB_ENA_MCAST_SUPPRESS_2_05 Enable libcoap library suppression of
205 multicast responses that are
empty (overridden by RFC7967
No-Response option) for multicast
requests.
COAP_RESOURCE_FLAGS_LIB_ENA_MCAST_SUPPRESS_2_XX Enable libcoap library suppressing
2.xx multicast responses (overridden
by RFC7967 No-Response option) for
multicast requests.
COAP_RESOURCE_FLAGS_LIB_DIS_MCAST_SUPPRESS_4_XX Disable libcoap library suppressing
4.xx multicast responses (overridden
by RFC7967 No-Response option) for
multicast requests.
COAP_RESOURCE_FLAGS_LIB_DIS_MCAST_SUPPRESS_5_XX Disable libcoap library suppressing
5.xx multicast responses (overridden
by RFC7967 No-Response option) for
multicast requests.
NOTE: uri_path, if not 7 bit readable ASCII, binary bytes must be hex encoded according to the rules
defined in "RFC3986 2.1. Percent-Encoding".
Function: coap_resource_unknown_init()
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.
Function: coap_resource_unknown_init2()
The coap_resource_unknown_init2() 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. flags can be zero or more of the
COAP_RESOURCE_FLAGS MCAST definitions.
Function: coap_resource_proxy_uri_init()
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, or the request has to be passed on to an upstream server.
Function: coap_resource_proxy_uri_init2()
The coap_resource_proxy_uri_init2() 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, or the request has to be passed on to an upstream server. flags can be zero or more
COAP_RESOURCE_FLAGS MCAST definitions.
Function: coap_add_resource()
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(), coap_resource_unknown_init2(),
coap_resource_proxy_uri_init() or coap_resource_proxy_uri_init2(). 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() will delete any previous resource with the same uri_path before adding in the new
resource.
Function: coap_delete_resource()
The coap_delete_resource() function deletes the resource identified by resource. The context parameter is
ignored. The storage allocated for that resource is freed, along with any attributes associated with the
resource.
Function: coap_resource_set_mode()
The coap_resource_set_mode() changes the unsolicited 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.
Function: coap_resource_set_userdata()
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.
Function: coap_resource_get_userdata()
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().
Function: coap_resource_release_userdata_handler()
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.
Function: coap_resource_get_uri_path()
The coap_resource_get_uri_path() function is used to obtain the UriPath of the resource definion.
RETURN VALUES
coap_resource_init(), coap_resource_unknown_init(), coap_resource_unknown_init2(),
coap_resource_proxy_uri_init() and coap_resource_proxy_uri_init2() return a newly created resource or
NULL if there is a malloc failure.
coap_delete_resource() returns 0 on failure (resource not found), 1 on success.
coap_resource_get_userdata() returns the value previously set by the coap_resource_set_userdata()
function or NULL.
coap_resource_get_uri_path() 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_request_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_request_handler(r, COAP_REQUEST_GET, hnd_get_time);
coap_register_request_handler(r, COAP_REQUEST_PUT, hnd_put_time);
coap_register_request_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(NULL, 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;
/*
* Get the specific resource being requested to determine what the response is
* 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_put_unknown(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_request_handler(r, COAP_REQUEST_PUT, hnd_put);
coap_register_request_handler(r, COAP_REQUEST_DELETE, hnd_delete);
/* We possibly want to Observe the GETs */
coap_resource_set_get_observable(r, 1);
coap_register_request_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_init2(hnd_put_unknown, 0);
/*
* Additional handlers can be added - for example
* coap_register_request_handler(r, COAP_REQUEST_POST, hnd_post_unknown);
* coap_register_request_handler(r, COAP_REQUEST_GET, hnd_get_unknown);
* coap_register_request_handler(r, COAP_REQUEST_DELETE, hnd_delete_unknown);
*/
coap_add_resource(ctx, r);
}
SEE ALSO
coap_attribute(3), coap_context(3), coap_handler(3) and coap_observe(3)
FURTHER INFORMATION
See
"RFC7252: The Constrained Application Protocol (CoAP)"
"RFC3986: Uniform Resource Identifier (URI): Generic Syntax"
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>
coap_resource 4.3.4 04/15/2024 COAP_RESOURCE(3)