1COAP_ATTRIBUTE(3) libcoap Manual COAP_ATTRIBUTE(3)
2
6 coap_attribute, coap_add_attr, coap_find_attr, coap_attr_get_value -
7 Work with CoAP attributes
8
10 #include <coap3/coap.h>
11 coap_attr_t *coap_add_attr(coap_resource_t *resource, coap_str_const_t
13 *name, coap_str_const_t *value, int flags);
14 coap_attr_t *coap_find_attr(coap_resource_t *resource, coap_str_const_t
16 *name);
17 coap_str_const_t *coap_attr_get_value(coap_attr_t *attribute);
19 For specific (D)TLS library support, link with -lcoap-3-notls,
21 -lcoap-3-gnutls, -lcoap-3-openssl, -lcoap-3-mbedtls or
22 -lcoap-3-tinydtls. Otherwise, link with -lcoap-3 to get the default
23 (D)TLS library support.
24
26 CoAP Resources on a CoAP Server need to be created, updated etc. The
27 URI in the request packet defines the resource to work with, with
28 possibly the Query referring to a sub-resource.
29 When resources are configured on the CoAP server, the URI to match
31 against is specified. Callback Handlers are then added to the resource
32 to handle the different request methods.
33 Adding Attributes allows textual information to be added to the
35 resource which can then be reported back to any client doing a Resource
36 Discovery using a "GET /.well-known/core" request with an optional
37 query. See "RFC6690 5. Examples" for some examples of resource
38 discovery usage. Common attribute names are rt, if, sz, ct, obs, rel,
39 anchor, rev, hreflang, media, title and type. href cannot be an
40 attribute name.
41 Attributes are automatically deleted when a Resource is deleted.
43
45 Function: coap_add_attr()
46 The coap_add_attr() function registers a new attribute called name for
48 the resource. The value of the attribute is value which can be NULL.
49 flags can be zero or more of the following or’d together, which, if
51 set, defines what is to be internally freed off when the attribute is
52 deleted with coap_delete_resource().
53 COAP_ATTR_FLAGS_RELEASE_NAME Free off name when
56 attribute is deleted with
57 coap_delete_resource().
58 COAP_ATTR_FLAGS_RELEASE_VALUE Free off value when
60 attribute is deleted with
61 coap_delete_resource().
62 Function: coap_find_attr()
65 The coap_find_attr() function returns the attribute with the name, if
67 found, associated with resource.
68 Function: coap_attr_get_value()
70 The coap_attr_get_value() function returns the value associated with
72 the specified attribute.
73
75 coap_add_attr() returns a pointer to the attribute that was created or
76 NULL if there is a malloc failure.
77 coap_find_attr() returns a pointer to the first matching attribute or
79 NULL if the name was not found.
80 coap_attr_get_value() returns a pointer to the value held within the
82 attribute. The pointer can be NULL if the value id NULL, or NULL if
83 attribute does not exist.
84
86 Initialize Resources
87 #include <coap3/coap.h>
89 void hnd_get_index(coap_resource_t *resource, coap_session_t *session,
91 const coap_pdu_t *request,
92 const coap_string_t *query,
93 coap_pdu_t *response);
94 void hnd_get_time(coap_resource_t *resource, coap_session_t *session,
96 const coap_pdu_t *request,
97 const coap_string_t *query,
98 coap_pdu_t *response);
99 void hnd_put_time(coap_resource_t *resource, coap_session_t *session,
101 const coap_pdu_t *request,
102 const coap_string_t *query,
103 coap_pdu_t *response);
104 void hnd_delete_time(coap_resource_t *resource, coap_session_t *session,
106 const coap_pdu_t *request,
107 const coap_string_t *query,
108 coap_pdu_t *response);
109 static void
111 init_resources(coap_context_t *ctx) {
112 coap_resource_t *r;
114 /* Create a resource to return general information */
116 r = coap_resource_init(NULL, 0);
117 coap_register_request_handler(r, COAP_REQUEST_GET, hnd_get_index);
118 /* Document resource for '.well-known/core' request */
120 coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
121 coap_add_attr(r, coap_make_str_const("title"),
122 coap_make_str_const("\"General Info\""), 0);
123 coap_add_resource(ctx, r);
125 /* Create a resource to return return or update time */
127 r = coap_resource_init(coap_make_str_const("time"),
128 COAP_RESOURCE_FLAGS_NOTIFY_CON);
129 coap_resource_set_get_observable(r, 1);
130 coap_register_request_handler(r, COAP_REQUEST_GET, hnd_get_time);
131 coap_register_request_handler(r, COAP_REQUEST_PUT, hnd_put_time);
132 coap_register_request_handler(r, COAP_REQUEST_DELETE, hnd_delete_time);
133 /* Document resource for 'time' request */
135 coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
136 coap_add_attr(r, coap_make_str_const("title"),
137 coap_make_str_const("\"Internal Clock\""), 0);
138 coap_add_attr(r, coap_make_str_const("rt"), coap_make_str_const("\"secs\""),
139 0);
140 coap_add_attr(r, coap_make_str_const("if"), coap_make_str_const("\"clock\""),
141 0);
142 coap_add_resource(ctx, r);
144 }
146
148 coap_resource(3) and coap_handler(3)
149
151 See
152 "RFC7252: The Constrained Application Protocol (CoAP)"
154 "RFC6690: Constrained RESTful Environments (CoRE) Link Format"
156 for further information.
158
160 Please report bugs on the mailing list for libcoap:
161 libcoap-developers@lists.sourceforge.net or raise an issue on GitHub at
162 https://github.com/obgm/libcoap/issues
163
165 The libcoap project <libcoap-developers@lists.sourceforge.net>
166coap_attribute 4.3.4 10/09/2023 COAP_ATTRIBUTE(3)