CoAP Node that simulates a being a temperature sensor. Written used libcoap library

termo.c

 /*	Sergio Maeso Jimenez
  * 	semaesoj@it.uc3m.es
  * 	03.08.2016
  * 	
  * 	coap code which simulates a temperature sensor
  * 	based on https://github.com/nikosft/libcoap/blob/master/piggybacked/server.c
  *
  *.  gcc -Wall -I /usr/local/include/coap -L /usr/local/lib termo.c -o termo -lcoap-1 -DWITH_POSIX
  */


// DO NOT FORGET export LD_LIBRARY_PATH=/usr/local/lib
//#include "dtls.h" 
#include "coap.h"	// /usr/local/include/coap
#include "stdio.h"
#include <time.h>

#define DEFAULT_PORT 5683

unsigned char fan = 0;
/*
 * get (simulate) mocked temperature readings
 *
 */

int getTemp(){
    srand(time(NULL));
    int r = rand() % 20 ; // rnd numb between 0 and 20
    return 20 + r; // rnd temp between 20 an 40
}
/*
 * The resource handler
 */ 
static void gettemp_handler(coap_context_t *cntx, struct coap_resource_t *resource, 
              const coap_endpoint_t *local_interface, coap_address_t *peer, 
              coap_pdu_t *request, str *token, coap_pdu_t *response) 
{
	unsigned char buf[8];
	char response_data[8];
	int temp = getTemp();
	printf("Sending Temp %d ºC\n",temp);
	sprintf(response_data, "%d", temp);
	response->hdr->code = COAP_RESPONSE_CODE(205);
	coap_add_option(response, COAP_OPTION_CONTENT_TYPE, coap_encode_var_bytes(buf, COAP_MEDIATYPE_TEXT_PLAIN), buf);
	coap_add_data  (response, strlen(response_data), (const unsigned char *)response_data);
}

static void deltemp_handler(coap_context_t *cntx, struct coap_resource_t *resource, 
              const coap_endpoint_t *local_interface, coap_address_t *peer, 
              coap_pdu_t *request, str *token, coap_pdu_t *response) 
{
	(void)cntx;
	(void)resource;
	(void)peer;
	(void)request;
	(void)token;
	(void)response;

}
static void gettime_handler(coap_context_t *cntx, struct coap_resource_t *resource, const coap_endpoint_t *local_interface, coap_address_t *peer, coap_pdu_t *request, str *token, coap_pdu_t *response) 
{
	char response_data[8];
	
	time_t timer;
	unsigned char buffer[26];
	struct tm* tm_info;

	time(&timer);
	tm_info = localtime(&timer);

	strftime((char *)buffer, 26, "%Y:%m:%d %H:%M:%S", tm_info);
	printf("Sending Time %s\n",buffer);
	sprintf(response_data, "%s", buffer);
	response->hdr->code = COAP_RESPONSE_CODE(205);
	coap_add_option(response, COAP_OPTION_CONTENT_TYPE, coap_encode_var_bytes(buffer, COAP_MEDIATYPE_TEXT_PLAIN), buffer);
	coap_add_data  (response, strlen(response_data), (const unsigned char *)response_data);
	

}
static void settime_handler(coap_context_t *cntx, struct coap_resource_t *resource, const coap_endpoint_t *local_interface, coap_address_t *peer, coap_pdu_t *request, str *token, coap_pdu_t *response) 
{

}

static void deltime_handler(coap_context_t *cntx, struct coap_resource_t *resource, 
              const coap_endpoint_t *local_interface, coap_address_t *peer, 
              coap_pdu_t *request, str *token, coap_pdu_t *response) 
{
	(void)cntx;
	(void)resource;
	(void)peer;
	(void)request;
	(void)token;
	(void)response;

}

void  setfan_handler(coap_context_t *cntx, struct coap_resource_t *resource, 
              const coap_endpoint_t *local_interface, coap_address_t *peer, 
              coap_pdu_t *request, str *token, coap_pdu_t *response) {
	
	size_t size;
	unsigned char *data;	      
	response->hdr->code = COAP_RESPONSE_CODE(204);
	coap_get_data(request, &size, &data);
	
	fan = atoi((char*)data);
	printf("Received %s -> %d\n",data,fan);
	if(fan>100)fan=100;

}

static void getfan_handler(coap_context_t *cntx, struct coap_resource_t *resource, 
              const coap_endpoint_t *local_interface, coap_address_t *peer, 
              coap_pdu_t *request, str *token, coap_pdu_t *response) 
{
	unsigned char buf[8];
	char response_data[8];
	printf("Sending Fan %d %%\n",fan);
	sprintf(response_data, "%d", fan);
	response->hdr->code = COAP_RESPONSE_CODE(205);
	coap_add_option(response, COAP_OPTION_CONTENT_TYPE, coap_encode_var_bytes(buf, COAP_MEDIATYPE_TEXT_PLAIN), buf);
	coap_add_data  (response, strlen(response_data), (const unsigned char *)response_data);
}

int main(int argc, char* argv[])
{	

	coap_context_t*  cntx;
	coap_address_t   serv_addr;
	coap_resource_t* temp_resource;
	coap_resource_t* time_resource;
	coap_resource_t* fan_resource;

	fd_set           readfds;    
	/* Prepare the CoAP server socket */ 
	coap_address_init(&serv_addr);
	serv_addr.addr.sin.sin_family      = AF_INET;
	serv_addr.addr.sin.sin_addr.s_addr = INADDR_ANY;
	serv_addr.addr.sin.sin_port        = htons(DEFAULT_PORT); //default port
	cntx                                = coap_new_context(&serv_addr);
	if (!cntx) exit(EXIT_FAILURE);
	
	/* Initialize the fan resource */ 
	fan_resource = coap_resource_init((unsigned char *)"fan", 3, 0);
	coap_register_handler(fan_resource, COAP_REQUEST_GET, getfan_handler);
	coap_register_handler(fan_resource, COAP_REQUEST_PUT, setfan_handler);
	coap_add_resource(cntx, fan_resource);
	
	/* Initialize the temperature resource */
	temp_resource = coap_resource_init((unsigned char *)"temperature", 11, 0);
	coap_register_handler(temp_resource, COAP_REQUEST_GET, gettemp_handler);
	coap_register_handler(temp_resource, COAP_REQUEST_DELETE, deltemp_handler);
	temp_resource->observable = 1;
	coap_add_attr(temp_resource, (unsigned char *)"ct", 2, (unsigned char *)"0", 1, 0);
	coap_add_attr(temp_resource, (unsigned char *)"title", 5, (unsigned char *)"\"CPU temperature\"", 16, 0);
	coap_add_resource(cntx, temp_resource);
	
	/* Initialize the temperature resource */
	time_resource = coap_resource_init((unsigned char *)"time", 4, 0);
	coap_register_handler(time_resource, COAP_REQUEST_GET, gettime_handler);
	coap_register_handler(time_resource, COAP_REQUEST_PUT, settime_handler);
	coap_register_handler(time_resource, COAP_REQUEST_DELETE, deltime_handler);
	coap_add_attr(time_resource, (unsigned char *)"ct", 2, (unsigned char *)"0", 1, 0);
	coap_add_attr(time_resource, (unsigned char *)"title", 5, (unsigned char *)"\"Internal Clock\"", 16, 0);
	coap_add_attr(time_resource, (unsigned char *)"rt", 2, (unsigned char *)"\"Ticks\"", 7, 0);
	coap_add_attr(time_resource, (unsigned char *)"if", 2, (unsigned char *)"\"clock\"", 7, 0);
	time_resource->observable = 1;
	coap_add_resource(cntx, time_resource);
		/*
   The Content-Format code "ct" attribute provides a hint about the Content-Formats
   this resource returns. Note that this is only a hint, and it does not
   override the Content-Format Option of
   a CoAP response obtained by actually requesting the representation of
   the resource.  The value is in the CoAP identifier code format as a
   decimal ASCII integer and MUST be in the range of 0-65535 (16-bit
   unsigned integer).  For example, "application/xml" would be indicated
   as "ct=41".  If no Content-Format code attribute is present, then
   nothing about the type can be assumed.  The Content-Format code
   attribute MAY include a space-separated sequence of Content-Format
   codes, indicating that multiple content-formats are available.

	 */
	
	/*Listen for incoming connections*/
	while (1) {
		FD_ZERO(&readfds);
		FD_SET( cntx->sockfd, &readfds );
		int result = select( FD_SETSIZE, &readfds, 0, 0, NULL );
		if (result<0) /* socket error */
		{
			exit(EXIT_FAILURE);
		} 
		else if ( result > 0 && FD_ISSET( cntx->sockfd, &readfds )) /* socket read*/
		{	 
				coap_read(cntx);       
		} 
	}    
}