'\" t
.\" Title: coap_block
.\" Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot
.\" Date: 10/28/2023
.\" Manual: libcoap Manual
.\" Source: coap_block 4.3.4
.\" Language: English
.\"
.TH "COAP_BLOCK" "3" "10/28/2023" "coap_block 4\&.3\&.4" "libcoap Manual"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
coap_block, coap_context_set_block_mode, coap_add_data_large_request, coap_add_data_large_response, coap_get_data_large, coap_block_build_body, coap_q_block_is_supported \- Work with CoAP Blocks
.SH "SYNOPSIS"
.sp
\fB#include \fR
.sp
\fBvoid coap_context_set_block_mode(coap_context_t *\fR\fB\fIcontext\fR\fR\fB, uint8_t \fR\fB\fIblock_mode\fR\fR\fB);\fR
.sp
\fBint coap_add_data_large_request(coap_session_t *\fR\fB\fIsession\fR\fR\fB, coap_pdu_t *\fR\fB\fIpdu\fR\fR\fB, size_t \fR\fB\fIlength\fR\fR\fB, const uint8_t *\fR\fB\fIdata\fR\fR\fB, coap_release_large_data_t \fR\fB\fIrelease_func\fR\fR\fB, void *\fR\fB\fIapp_ptr\fR\fR\fB);\fR
.sp
\fBint coap_add_data_large_response(coap_resource_t *\fR\fB\fIresource\fR\fR\fB, coap_session_t *\fR\fB\fIsession\fR\fR\fB, const coap_pdu_t *\fR\fB\fIrequest\fR\fR\fB, coap_pdu_t *\fR\fB\fIresponse\fR\fR\fB, const coap_string_t *query, uint16_t \fR\fB\fImedia_type\fR\fR\fB, int \fR\fB\fImaxage\fR\fR\fB, uint64_t etag, size_t \fR\fB\fIlength\fR\fR\fB, const uint8_t *\fR\fB\fIdata\fR\fR\fB, coap_release_large_data_t \fR\fB\fIrelease_func\fR\fR\fB, void *\fR\fB\fIapp_ptr\fR\fR\fB);\fR
.sp
\fBint coap_get_data_large(const coap_pdu_t *\fR\fB\fIpdu\fR\fR\fB, size_t *\fR\fB\fIlength, const uint8_t **_data\fR\fR\fB, size_t *\fR\fB\fIoffset\fR\fR\fB, size_t *\fR\fB\fItotal\fR\fR\fB);\fR
.sp
\fBcoap_binary_t *coap_block_build_body(coap_binary_t *\fR\fB\fIbody_data\fR\fR\fB, size_t \fR\fB\fIlength\fR\fR\fB, const uint8_t *\fR\fB\fIdata\fR\fR\fB, size_t \fR\fB\fIoffset\fR\fR\fB, size_t \fR\fB\fItotal\fR\fR\fB);\fR
.sp
\fBint coap_q_block_is_supported(void);\fR
.sp
For specific (D)TLS library support, link with \fB\-lcoap\-3\-notls\fR, \fB\-lcoap\-3\-gnutls\fR, \fB\-lcoap\-3\-openssl\fR, \fB\-lcoap\-3\-mbedtls\fR or \fB\-lcoap\-3\-tinydtls\fR\&. Otherwise, link with \fB\-lcoap\-3\fR to get the default (D)TLS library support\&.
.SH "DESCRIPTION"
.sp
Regular setting up of a PDU and transmission is covered in \fBcoap_pdu_setup\fR(3) where all the payload data can fit in a single packet\&. This man page covers how to work with PDUs where the overall body of information may need to be split across several packets by using CoAP Block\-Wise Transfers (RFC7959 and RFC9177)\&.
.sp
The block\-wise transfers can be controlled by the application, or libcoap is instructed to do all the requests for the next blocks and only present the final body of the result to the application\&. In summary, the following three ways handle processing a body of data that has to be split across multiple payloads (blocks)\&.
.sp
.RS 4
.ie n \{\
\h'-04' 1.\h'+01'\c
.\}
.el \{\
.sp -1
.IP " 1." 4.2
.\}
Application does all the work
It is the responsibility of the application to analyze each block transmission at receipt and then generate the next request as per
RFC7959\&. In this case,
\fBcoap_context_set_block_mode\fR() function must not be called to maintain backward compatibility with applications that did the block handling within the application\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04' 2.\h'+01'\c
.\}
.el \{\
.sp -1
.IP " 2." 4.2
.\}
Application sees individual blocks
By calling
\fBcoap_context_set_block_mode(context, COAP_BLOCK_USE_LIBCOAP)\fR
and using the appropriate functions, the requests for the next block of data is handled automatically by the libcoap layer\&. Each individual block of data is presented to the application for processing\&.
By calling
\fBcoap_get_data_large\fR(), the application can determine if this is the first block or not (using
\fIoffset\fR
value), whether the first block is all the data (\fIoffset\fR
= 0,
\fIlength\fR
=
\fItotal\fR) and whether this is the last block (\fIoffset\fR
+
\fIlength\fR
=
\fItotal\fR)\&. It is the responsibility of the application to re\-assemble the individual blocks into a single body of data\&.
\fBNOTE:\fR
\fItotal\fR
is only an approximation (it will be >
\fIoffset\fR
+
\fIlength\fR) until the final block is received\&.
If this is the request handler in a server, the server still needs to return a COAP_RESPONSE_CODE_CONTINUE 2\&.31 (Continue) response code if the received data is not for the final block, otherwise a COAP_RESPONSE_CODE_CREATED 2\&.01 (Created) or COAP_RESPONSE_CODE_CHANGED 2\&.04 (Changed) should be returned\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04' 3.\h'+01'\c
.\}
.el \{\
.sp -1
.IP " 3." 4.2
.\}
Application only sees all of the body
By calling
\fBcoap_context_set_block_mode(context, COAP_BLOCK_USE_LIBCOAP|COAP_BLOCK_SINGLE_BODY)\fR
and using the appropriate functions, the requests for all the blocks of data is handled automatically by the libcoap layer\&. Only the complete body of the data is presented to the application, unless there is an error\&.
\fBcoap_get_data_large\fR() will only return the entire body of data (\fIoffset\fR
always 0,
\fIlength\fR
=
\fItotal\fR) and there is no need to re\-assemble individual blocks into a large body of data\&.
In RAM constrained environments, option 2 may be the preferred method\&.
.RE
.sp
This man page focuses on getting libcoap to do all the work, not how to do it all in the application\&.
.sp
However, if the client supplies a Block1 or Block2 Option in the PDU where the block number is not 0, this is assumed to be a random access request and any other blocks will not be requested by libcoap even if instructed otherwise\&.
.sp
The functions that are named \fB_large\fR are intended as replacements for the equivalent functions as described in \fBcoap_pdu_setup\fR(3)\&.
.SH "CALLBACK HANDLER"
.sp
\fBCallback Type: coap_release_large_data_t\fR
.sp
.if n \{\
.RS 4
.\}
.nf
/**
* Callback handler for de\-allocating the data based on @p app_ptr provided to
* coap_add_data_large_*() functions following transmission of the supplied
* data\&.
*
* @param session The session that this data is associated with
* @param app_ptr The application provided pointer to the
* coap_add_data_large_*() functions
*/
typedef void (*coap_release_large_data_t)(coap_session_t *session,
void *app_ptr);
.fi
.if n \{\
.RE
.\}
.SH "FUNCTIONS"
.sp
\fBFunction: coap_context_set_block_mode()\fR
.sp
The \fBcoap_context_set_block_mode\fR() function is used to set up the \fIcontext\fR level \fIblock_mode\fR block handling bits for supporting RFC7959 \fIblock_mode\fR flows down to a session when a session is created and if the peer does not support the respective block mode, an appropriate bit may get disabled in the session \fIblock_mode\fR\&.
.sp
.if n \{\
.RS 4
.\}
.nf
#define COAP_BLOCK_USE_LIBCOAP 0x01 /* Use libcoap to do block requests */
#define COAP_BLOCK_SINGLE_BODY 0x02 /* Deliver the data as a single body */
#define COAP_BLOCK_TRY_Q_BLOCK 0x04 /* Try Q\-Block method */
#define COAP_BLOCK_USE_M_Q_BLOCK 0x08 /* Use M bit when recovering Q\-Block2 */
#define COAP_BLOCK_NO_PREEMPTIVE_RTAG 0x10 /* Don\*(Aqt use pre\-emptive Request\-Tags */
.fi
.if n \{\
.RE
.\}
.sp
\fIblock_mode\fR is an or\(cqd set of zero or more COAP_BLOCK_* definitions\&.
.sp
If \fBCOAP_BLOCK_USE_LIBCOAP\fR is not set, then everything works as per Option 1 above\&.
.sp
If \fBCOAP_BLOCK_SINGLE_BODY\fR is set, then the entire body of data is presented to the receiving handler, otherwise each individual block is presented on arrival\&. To obtain the data, length and current offset, \fBcoap_get_data_large\fR() must be used instead of \fBcoap_get_data\fR()\&. It may be appropriate not to set \fBCOAP_BLOCK_SINGLE_BODY\fR if there are RAM limitations\&.
.sp
\fBNOTE:\fR It is the responsibility of the receiving application to re\-assemble the \fIdata\fR as appropriate (e\&.g\&., using \fBcoap_block_build_body\fR()) if \fBCOAP_BLOCK_SINGLE_BODY\fR is not set\&.
.sp
\fBNOTE:\fR If \fBCOAP_BLOCK_SINGLE_BODY\fR is not set, then the CoAP server on receiving request data that is split over multiple data blocks must respond with COAP_RESPONSE_CODE_CONTINUE 2\&.31 (Continue) response code if the received data is not for the final block, otherwise a COAP_RESPONSE_CODE_CREATED 2\&.01 (Created) or COAP_RESPONSE_CODE_CHANGED 2\&.04 (Changed) should be returned\&.
.sp
To indicate support for Q\-Block\-1 and Q\-Block2, \fBCOAP_BLOCK_TRY_Q_BLOCK\fR needs to be set on both the client and server\&. \fBCOAP_BLOCK_SINGLE_BODY\fR is assumed to be set if using Q\-Block as the data will always be presented as a single body\&. If \fBCOAP_BLOCK_USE_M_Q_BLOCK\fR is defined, then the \fIM\fR bit version of recovery will be used if possible\&.
.sp
If \fBCOAP_BLOCK_USE_LIBCOAP\fR is set, then any PDUs presented to the application handlers will get the tokens set back to the initiating token so that requests can be matched with responses even if different tokens had to be used for the series of packet interchanges\&. Furthermore, if \fBCOAP_BLOCK_SINGLE_BODY\fR is set, then the PDU that presents the entire body will have any BlockX or Q\-BlockX option removed\&.
.sp
\fBNOTE:\fR \fBCOAP_BLOCK_USE_LIBCOAP\fR must be set if libcoap is to do all the block tracking and requesting, otherwise the application will have to do all of this work (the default if \fBcoap_context_set_block_mode\fR() is not called)\&.
.sp
If \fBCOAP_BLOCK_NO_PREEMPTIVE_RTAG\fR is set, then Request\-Tag options are only sent when a large amount of data is being sent to the server using the Block1 option\&. Otherwise, a Request\-Tag option is sent with any request (apart from DELETE) on the off chance that there may be multiple Block2 based responses for multiple requests to the same resource that need to be differentiated between\&.
.sp
\fBFunction: coap_add_data_large_request()\fR
.sp
The \fBcoap_add_data_large_request\fR() function is similar to \fBcoap_add_data\fR(), but supports the transmission of data that has a body size that is potentially larger than can be fitted into a single client request PDU\&. The specified payload \fIdata\fR of length \fIlength\fR is associated with the \fIsession\fR with the first block of data added to the PDU \fIpdu\fR along with the appropriate CoAP options such as (Q\-)Block1, Size1 and Request\-Tag if the data does not fit in a single PDU\&.
.sp
When the block receipt has been acknowledged by the peer, the library will then send the next block of data until all the data has been transmitted\&.
.sp
The \fIdata\fR passed to the function \fBcoap_add_data_large_request\fR() must exist until all blocks have been transmitted\&. The callback function \fIrelease_func\fR can be used to release storage that has been dynamically allocated to hold the transmit data\&. If not NULL, the callback function is called once the final block of \fIdata\fR has been transmitted\&. The user\-defined parameter \fIapp_ptr\fR is the same value that was passed to \fBcoap_add_data_large_request\fR()\&.
.sp
\fBNOTE:\fR This function must only be called once per \fIpdu\fR\&.
.sp
\fBNOTE:\fR Options cannot be added to the \fIpdu\fR after coap_add_data_large_request() is called\&.
.sp
\fBFunction: coap_add_data_large_response()\fR
.sp
The \fBcoap_add_data_large_response\fR() function is responsible for handling the server\(cqs large responses to requests\&. \fBcoap_add_data_large_response\fR() should be used as a direct replacement for \fBcoap_add_data\fR() if it is possible that the \fIlength\fR of \fIdata\fR will not fit in a single server\(cqs response pdu\&. This function adds in the initial part of the payload \fIdata\fR of length \fIlength\fR to the PDU \fIpdu\fR\&.
.sp
The \fIdata\fR passed to the function \fBcoap_add_data_large_response\fR() must exist until all blocks have been transmitted\&. The callback function \fIrelease_func\fR can be used to release storage that has been dynamically allocated to hold the transmit data\&. If not NULL, the callback function is called once the final block of \fIdata\fR has been transmitted\&. The user\-defined parameter \fIapp_ptr\fR is the same value that was passed to \fBcoap_add_data_large_response\fR()\&.
.sp
It also adds in the appropriate CoAP options such as Block2, Size2 and ETag to handle block\-wise transfer if the data does not fit in a single PDU\&.
.sp
\fIresource\fR, \fIquery\fR, \fIsession\fR, \fIrequest\fR, and \fIresponse\fR are the same parameters as in the called resource handler that invokes \fBcoap_add_data_large_response\fR()\&. If \fIetag\fR is 0, then a unique ETag value will be generated, else is the ETag value to use\&. The \fImedia_type\fR is for the format of the \fIdata\fR and \fImaxage\fR defines the lifetime of the response\&. If \fImaxage\fR is set to \-1, then the Max\-Age option does not get included (which indicates the default value of 60 seconds according to "RFC7252 5\&.6\&.1\&. Freshness Model")\&.
.sp
The application request handler for the resource is only called once instead of potentially multiple times\&.
.sp
\fBNOTE:\fR This function must only be called once per \fIpdu\fR\&.
.sp
\fBNOTE:\fR Options cannot be added to the \fIpdu\fR after coap_add_data_large_request() is called\&.
.sp
\fBFunction: coap_get_data_large()\fR
.sp
The \fBcoap_get_data_large\fR() function is used abstract from the \fIpdu\fR information about the received data by updating \fIlength\fR with the length of data available, \fIdata\fR with a pointer to where the data is located, \fIoffset\fR with where this block of data starts and \fItotal\fR with the total amount of data\&. \fIoffset\fR will always be zero if block_mode includes COAP_BLOCK_SINGLE_BODY\&. All of the body\(cqs data has been received if "\fIoffset\fR + \fIlength\fR == \fItotal\fR"\&.
.sp
\fBNOTE:\fR \fItotal\fR is potentially only an indication of the total size of the body and is only exact when all of the data has been received\&.
.sp
\fBFunction: coap_block_build_body()\fR
.sp
The \fBcoap_block_build_body\fR() function is used to re\-assemble the received data as returned by \fBcoap_get_data_large\fR() into a single blob of data\&. Data from \fIdata\fR of length \fIlength\fR starting from offset \fIoffset\fR is added to \fIbody_data\fR\&. The resultant state of \fIbody_data\fR is returned\&. If \fIbody_data\fR is NULL, or \fItotal\fR is larger than the current size of \fIbody_data\fR, then \fIbody_data\fR is re\-allocated and returned\&. If there is an error, \fIbody_data\fR gets de\-allocated\&.
.sp
If \fIblock_mode\fR (as set by \fBcoap_context_set_block_mode\fR()) includes COAP_BLOCK_SINGLE_BODY, then the request/response handler will only get called once with the entire body containing the data from all of the individual blocks\&. If there is a change of data during the blocks receipt (e\&.g\&., ETag value changes), then the entire set of data is re\-requested and the partial body dropped\&.
.sp
\fBFunction: coap_q_block_is_supported()\fR
.sp
The \fBcoap_q_block_is_supported\fR() function is used to determine whether libcoap has been build with Q\-Block support or not\&.
.SH "RETURN VALUES"
.sp
\fBcoap_add_data_large_request\fR(), \fBcoap_add_data_large_response\fR(), and \fBcoap_get_data_large\fR() return 0 on failure, 1 on success\&.
.sp
\fBcoap_block_build_body\fR() returns the current state of the body\(cqs data (which may have some missing gaps) or NULL on error\&.
.sp
\fBcoap_q_block_is_supported\fR() returns 0 on failure, 1 on success\&.
.SH "EXAMPLES"
.sp
\fBSetup PDU and Transmit\fR
.sp
.if n \{\
.RS 4
.\}
.nf
#include
static int
build_send_pdu(coap_context_t *context, coap_session_t *session,
uint8_t msgtype, uint8_t request_code, const char *uri, const char *query,
unsigned char *data, size_t length, int observe) {
coap_pdu_t *pdu;
uint8_t buf[1024];
size_t buflen;
uint8_t *sbuf = buf;
int res;
coap_optlist_t *optlist_chain = NULL;
/* Remove (void) definition if variable is used */
(void)context;
/* Create the pdu with the appropriate options */
pdu = coap_pdu_init(msgtype, request_code, coap_new_message_id(session),
coap_session_max_pdu_size(session));
if (!pdu)
return 0;
/*
* Create unique token for this request for handling unsolicited /
* delayed responses
*/
coap_session_new_token(session, &buflen, buf);
if (!coap_add_token(pdu, buflen, buf)) {
coap_log_debug("cannot add token to request\en");
goto error;
}
if (uri) {
/* Add in the URI options */
buflen = sizeof(buf);
res = coap_split_path((const uint8_t*)uri, strlen(uri), sbuf, &buflen);
while (res\-\-) {
if (!coap_insert_optlist(&optlist_chain,
coap_new_optlist(COAP_OPTION_URI_PATH,
coap_opt_length(sbuf), coap_opt_value(sbuf))))
goto error;
sbuf += coap_opt_size(sbuf);
}
}
if (query) {
/* Add in the QUERY options */
buflen = sizeof(buf);
res = coap_split_query((const uint8_t*)query, strlen(query), sbuf, &buflen);
while (res\-\-) {
if (!coap_insert_optlist(&optlist_chain,
coap_new_optlist(COAP_OPTION_URI_QUERY,
coap_opt_length(sbuf), coap_opt_value(sbuf))))
goto error;
sbuf += coap_opt_size(sbuf);
}
}
if (request_code == COAP_REQUEST_GET && observe) {
/* Indicate that we want to observe this resource */
if (!coap_insert_optlist(&optlist_chain,
coap_new_optlist(COAP_OPTION_OBSERVE,
coap_encode_var_safe(buf, sizeof(buf),
COAP_OBSERVE_ESTABLISH), buf)
))
goto error;
}
/* \&.\&.\&. Other code / options etc\&. \&.\&.\&. */
/* Add in all the options (after internal sorting) to the pdu */
if (!coap_add_optlist_pdu(pdu, &optlist_chain))
goto error;
if (data && length) {
/* Add in the specified data */
if (!coap_add_data_large_request(session, pdu, length, data, NULL, NULL))
goto error;
}
if (coap_send(session, pdu) == COAP_INVALID_MID)
goto error;
return 1;
error:
if (pdu)
coap_delete_pdu(pdu);
return 0;
}
int
main(int argc, char *argv[]) {
coap_context_t *context = NULL;
coap_session_t *session = NULL;
unsigned char *data = NULL;
size_t data_length = 0;
(void)argc;
(void)argv;
/* Initialize libcoap library */
coap_startup();
/* \&.\&.\&. Set up context, session etc\&. \&.\&.\&. */
/* Set up using libcoap to do the block work */
coap_context_set_block_mode(context,
COAP_BLOCK_USE_LIBCOAP | COAP_BLOCK_SINGLE_BODY);
/* \&.\&.\&. Other code etc\&. \&.\&.\&. */
/* \&.\&. build data and define data_length \&.\&.\&. */
build_send_pdu(context, session, COAP_MESSAGE_CON, COAP_REQUEST_PUT,
"/example/uri", NULL, data, data_length, 0);
/* \&.\&.\&. Other code etc\&. \&.\&.\&. */
coap_cleanup();
return 0;
}
.fi
.if n \{\
.RE
.\}
.sp
\fBResource Request Handler Response PDU Update\fR
.sp
.if n \{\
.RS 4
.\}
.nf
#include
#include
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) {
unsigned char buf[40];
size_t len;
time_t now;
/* \&.\&.\&. Additional analysis code for resource, request pdu etc\&. \&.\&.\&. */
/* After analysis, generate a failure response and return if needed */
now = time(NULL);
if (query != NULL && coap_string_equal(query, coap_make_str_const("secs"))) {
/* Output secs since Jan 1 1970 */
len = snprintf((char *)buf, sizeof(buf), "%lu", now);
}
else {
/* Output human\-readable time */
struct tm *tmp;
tmp = gmtime(&now);
if (!tmp) {
/* If \*(Aqnow\*(Aq is not valid */
coap_pdu_set_code(response, COAP_RESPONSE_CODE_NOT_FOUND);
return;
}
len = strftime((char *)buf, sizeof(buf), "%b %d %H:%M:%S", tmp);
}
coap_pdu_set_code(response, COAP_RESPONSE_CODE_CONTENT);
/*
* Invoke coap_add_data_large_response() to do all the hard work\&.
* [A good practice, even though ins this case, the amount of data is small]
*
* Define the format \- COAP_MEDIATYPE_TEXT_PLAIN \- to add in
* Define how long this response is valid for (secs) \- 1 \- to add in\&.
*
* Observe Option added internally if needed within the function
* Block2 Option added internally if output too large
* Size2 Option added internally
* ETag Option added internally
*/
coap_add_data_large_response(resource, session, request, response,
query, COAP_MEDIATYPE_TEXT_PLAIN, 1, 0,
len,
buf,
NULL, NULL);
/*
* When request handler returns, the response pdu will get automatically
* sent, unless the pdu code is not updated and this is a NON or TCP based
* request\&.
*/
}
int
main(int argc, char *argv[]) {
coap_context_t *context = NULL;
coap_resource_t *r;
coap_resource_t *time_resource;
int not_exit = 1;
/* Initialize libcoap library */
coap_startup();
(void)argc;
(void)argv;
/* \&.\&.\&. Set up context etc\&. \&.\&.\&. */
/* Set up using libcoap to do the block work */
coap_context_set_block_mode(context,
COAP_BLOCK_USE_LIBCOAP | COAP_BLOCK_SINGLE_BODY);
/* Create a resource to return 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);
/* Document resource for \*(Aqtime\*(Aq 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(context, r);
time_resource = r;
/* \&.\&.\&. Loop waiting for incoming traffic \&.\&.\&. */
while (!not_exit) {
coap_io_process(context, 1000);
/* Cause a notification to anyone Observing \*(Aqtime\*(Aq */
coap_resource_notify_observers(time_resource, NULL);
}
/* Clean up */
coap_free_context(context);
coap_cleanup();
}
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBcoap_init\fR(3) \fBcoap_pdu_setup\fR(3), \fBcoap_observe\fR(3), and \fBcoap_resource\fR(3)
.SH "FURTHER INFORMATION"
.sp
See
.sp
"RFC7252: The Constrained Application Protocol (CoAP)"
.sp
"RFC7959: Block\-Wise Transfers in the Constrained Application Protocol (CoAP)"
.sp
for further information\&.
.SH "BUGS"
.sp
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
.SH "AUTHORS"
.sp
The libcoap project