--- name: "coap_resource_init" section: "3" platform: "linux" package: "libcoap3t64" version: "4.3.4-1.1+deb13u3" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/coap_resource" --- # coap\_resource\_init(3) Work with CoAP resources Part of [coap\_resource(3)](/coap_resource/3.md). ## 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 \** **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)](/coap_register_request_handler/3.md) 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)](/coap_add_attr/3.md) 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)](/coap_observe/3.md). **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)](/coap_observe/3.md). **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)](/coap_observe/3.md). **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 #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 /* 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_attribute/3.md), [**coap\_context**(3)](/coap_context/3.md), [**coap\_handler**(3)](/coap_handler/3.md) and [**coap\_observe**(3)](/coap_observe/3.md) ## 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 \