'\" t
.\" Title: coap_resource
.\" Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot
.\" Date: 05/14/2022
.\" Manual: libcoap Manual
.\" Source: coap_resource 4.2.1
.\" Language: English
.\"
.TH "COAP_RESOURCE" "3" "05/14/2022" "coap_resource 4\&.2\&.1" "libcoap Manual"
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.nh
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.SH "NAME"
coap_resource, coap_resource_init, coap_resource_unknown_init, coap_add_resource, coap_delete_resource, coap_delete_all_resources, coap_resource_set_mode \- Work with CoAP resources
.SH "SYNOPSIS"
.sp
\fB#include \fR
.sp
\fBcoap_resource_t *coap_resource_init(coap_str_const_t *\fR\fB\fIuri_path\fR\fR\fB, int \fR\fB\fIflags\fR\fR\fB);\fR
.sp
\fBcoap_resource_t *coap_resource_unknown_init(coap_method_handler_t \fR\fB\fIput_handler\fR\fR\fB);\fR
.sp
\fBvoid coap_add_resource(coap_context_t *\fR\fB\fIcontext\fR\fR\fB, coap_resource_t *\fR\fB\fIresource\fR\fR\fB);\fR
.sp
\fBint coap_delete_resource(coap_context_t \fR\fB\fIcontext\fR\fR\fB, coap_resource_t \fR\fB\fIresource\fR\fR\fB);\fR
.sp
\fBvoid coap_delete_all_resources(coap_context_t *\fR\fB\fIcontext\fR\fR\fB);\fR
.sp
\fBvoid coap_resource_set_mode(coap_resource_t *\fR\fB\fIresource\fR\fR\fB, int \fR\fB\fImode\fR\fR\fB);\fR
.sp
Link with \fB\-lcoap\-2\fR, \fB\-lcoap\-2\-gnutls\fR, \fB\-lcoap\-2\-openssl\fR or \fB\-lcoap\-2\-tinydtls\fR depending on your (D)TLS library type\&.
.SH "DESCRIPTION"
.sp
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\&.
.sp
When resources are configured on the CoAP server, the URI to match against in the request packet is specified\&.
.sp
Callback Handlers are then added to the resource to handle the different request methods\&.
.sp
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\&.
.sp
If an incoming packet request matches a resource\(cqs 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\&.
.sp
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\&.
.sp
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\&.
.sp
The \fBcoap_resource_init\fR() function returns a newly created \fIresource\fR of type \fIcoap_resource_t\fR * \&. \fIuri_path\fR specifies the uri string path to match against\&. \fIflags\fR is used to define whether the \fIresource\fR is of type Confirmable Message or Non\-Confirmable Message for any "observe" responses\&. See \fBcoap_observe\fR(3)\&. \fIflags\fR can be one of the following definitions or\(cqed together\&.
.TS
tab(:);
lt lt
lt lt
lt lt.
T{
.sp
\fBCOAP_RESOURCE_FLAGS_NOTIFY_NON\fR
T}:T{
.sp
Set the notification message type to non\-confirmable for any trigggered "observe" responses\&.
T}
T{
.sp
\fBCOAP_RESOURCE_FLAGS_NOTIFY_CON\fR
T}:T{
.sp
Set the notification message type to confirmable for any trigggered "observe" responses\&.
T}
T{
.sp
\fBCOAP_RESOURCE_FLAGS_RELEASE_URI\fR
T}:T{
.sp
Free off the coap_str_const_t for \fIuri_path\fR when the \fIresource\fR is deleted\&.
T}
.TE
.sp 1
.sp
\fBNOTE:\fR \fIuri_path\fR, if not 7 bit readable ASCII, binary bytes must be hex encoded according to the rules defined in RFC3968 Section 2\&.1\&.
.sp
The \fBcoap_resource_unknown_init\fR() returns a newly created \fIresource\fR of type \fIcoap_resource_t\fR *\&. \fIput_handler\fR is automatically added to the \fIresource\fR to handle PUT requests to resources that are unknown\&. Additional handlers can be added to this resource if required\&.
.sp
The \fBcoap_add_resource\fR() function registers the given \fIresource\fR with the \fIcontext\fR\&. The \fIresource\fR must have been created by \fBcoap_resource_init\fR(), or \fBcoap_resource_unknown_init\fR()\&. The storage allocated for the \fIresource\fR will be released by \fBcoap_delete_resource\fR()\&.
.sp
As the \fIuri_path\fR of the resource has to be unique across all of the resources associated with a \fIcontext\fR, \fBcoap_add_resource\fR() (or \fBcoap_add_resource_release\fR()) will delete any previous \fIresource\fR with the same \fIuri_path\fR before adding in the new \fIresource\fR\&.
.sp
The \fBcoap_delete_resource\fR() function deletes a \fIresource\fR identified by \fIresource\fR from \fIcontext\fR\&. The storage allocated for that \fIresource\fR is freed, along with any attrigutes associated with the \fIresource\fR\&.
.sp
The \fBcoap_delete_all_resources\fR() function deletes all resources from \fIcontext\fR and frees their storage\&.
.sp
The \fBcoap_resource_set_mode\fR() changes the notification message type of \fIresource\fR to the given \fImode\fR which must be one of COAP_RESOURCE_FLAGS_NOTIFY_NON or COAP_RESOURCE_FLAGS_NOTIFY_CON\&.
.SH "RETURN VALUES"
.sp
The \fBcoap_resource_init\fR() and \fBcoap_resource_unknown_init\fR() functions return a newly created resource or NULL if there is a malloc failure\&.
.sp
The \fBcoap_delete_resource\fR() function return 0 on failure (\fIresource\fR not found), 1 on success\&.
.SH "EXAMPLES"
.sp
\fBFixed Resources Set Up\fR
.sp
.if n \{\
.RS 4
.\}
.nf
#include
#define INDEX "This is an example server using libcoap\en"
void
hnd_get_index(coap_context_t *ctx, 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[3];
response\->code = COAP_RESPONSE_CODE(205);
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);
}
void
hnd_delete_time(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
/* \&.\&. code \&.\&. */
}
void
hnd_get_time(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
/* \&.\&. code \&.\&. */
}
void
hnd_put_time(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
/* \&.\&. code \&.\&. */
}
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("\e"General Info\e""), 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 \&.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("\e"Internal Clock\e""), 0);
coap_add_attr(r, coap_make_str_const("rt"), coap_make_str_const("\e"secs\e""),
0);
coap_add_attr(r, coap_make_str_const("if"), coap_make_str_const("\e"clock\e""),
0);
coap_add_resource(ctx, r);
}
.fi
.if n \{\
.RE
.\}
.sp
\fBDynamic Resources Set Up\fR
.sp
.if n \{\
.RS 4
.\}
.nf
#include
/* Regular DELETE handler \- used by resources created by the
* Unknown Resource PUT handler */
void
hnd_delete(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
/* \&.\&. code \&.\&. */
/* Dynamic resource no longer required \- delete it */
coap_delete_resource(ctx, resource);
}
/* Regular GET handler \- used by resources created by the
* Unknown Resource PUT handler */
void
hnd_get(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
coap_str_const_t *get_uri_path;
coap_string_t *get_query;
coap_opt_iterator_t opt_iter;
coap_opt_filter_t filter;
coap_opt_t *option;
int len;
/*
* 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);
get_query = query;
/* \&.\&. code \&.\&. */
}
/* Regular PUT handler \- used by resources created by the
* Unknown Resource PUT handler */
void
hnd_put(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
coap_string_t *put_uri_path;
/* get the uri_path */
put_uri_path = coap_get_uri_path(request);
if (!put_uri_path) {
response\->code = COAP_RESPONSE_CODE(404);
return;
}
/* \&.\&. code \&.\&. */
/* Need to do this as coap_get_uri_path() created it */
coap_delete_string(put_uri_path);
}
/* Unknown Resource PUT handler */
void
hnd_unknown_put(coap_context_t *ctx, coap_resource_t *resource,
coap_session_t *session, coap_pdu_t *request, coap_string_t *token,
coap_string_t *query, coap_pdu_t *response) {
coap_resource_t *r;
int len;
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) {
response\->code = COAP_RESPONSE_CODE(404);
return;
}
/* Check if new URI Path is valid */
if (!check_url_fn (uri_path, request\->code)) {
response\->code = COAP_RESPONSE_CODE(404);
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(ctx, r);
/* Do the PUT for this first call */
hnd_put(ctx, r, session, request, token, 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);
}
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBcoap_attribute\fR(3), \fBcoap_context\fR(3), \fBcoap_observe\fR(3) and \fBcoap_handler\fR(3)
.SH "FURTHER INFORMATION"
.sp
See "RFC7252: The Constrained Application Protocol (CoAP)" for further information\&.
.SH "BUGS"
.sp
Please report bugs on the mailing list for libcoap: libcoap\-developers@lists\&.sourceforge\&.net
.SH "AUTHORS"
.sp
The libcoap project