serverWithObserve.ino File Reference

A CoAP server with Observe functionality. More...

#include <Ethernet.h>
#include <EthernetUdp.h>
#include <ProsecCoAP.h>

Macros
#define	ENABLE_SERIAL_DEBUG   1
#define	SERIAL_BEGIN(baud)
#define	SERIAL_WHILE_WAIT
#define	SERIAL_PRINT(...)
#define	SERIAL_PRINTLN(...)
#define	SERIAL_WRITE(...)
#define	DEVICE_ID   1

Functions
IPAddress	ip (192, 168, 0, DEVICE_ID)
IPAddress	dns (0, 0, 0, 0)
IPAddress	gateway (0, 0, 0, 0)
IPAddress	subnet (255, 255, 255, 0)
void	timeCallback (Coap::Message &message, IPAddress ip, uint16_t port)
	Declaration of our callback to liked to the "time" resource.
void	setup ()
void	loop ()
Coap::Message	getCurrentTimeMessage ()
	Helper to build the time message.
void	sendNotification ()

Variables
EthernetUDP	Udp
Coap::Node	coapNode (Udp)
Coap::ObserverRegistry< 5 >	myObservers
byte	mac [] = {0xBE, 0xEF, 0xBE, 0xEF, 0x00, DEVICE_ID}

Detailed Description

A CoAP server with Observe functionality.

Author: Pasquale Lafiosca (2026)

Testing with libcoap

To test this example with the coap-client tool from libcoap:

coap-client-notls -p 5683 -v 9 -s 60 coap://192.168.0.1/time

You will see binary data incoming. Adjust IP address and port as needed.

Note that the option -s 60 will set the CoAP observe register option and keep the command running to receive notifications for the given amount of seconds.

Notes:

• -p 5683 sets a fixed port.
• -T AAAA optionally sets a fixed starting token (ASCII, libcoap will use the next one).

Multiple subscriptions with equal IP, port, path and token will result in the same observer.

Macro Definition Documentation

DEVICE_ID

#define DEVICE_ID   1

ENABLE_SERIAL_DEBUG

#define ENABLE_SERIAL_DEBUG   1

SERIAL_BEGIN

#define SERIAL_BEGIN

(

baud

)

Value:

Serial.begin(baud)

SERIAL_PRINT

#define SERIAL_PRINT

(

...

)

Value:

Serial.print(__VA_ARGS__)

SERIAL_PRINTLN

#define SERIAL_PRINTLN

(

...

)

Value:

Serial.println(__VA_ARGS__)

SERIAL_WHILE_WAIT

#define SERIAL_WHILE_WAIT

Value:

    while (!Serial)       \
    {                     \
        delay(10);        \
    }

SERIAL_WRITE

#define SERIAL_WRITE

(

...

)

Value:

Serial.write(__VA_ARGS__)

Function Documentation

dns()

IPAddress dns	(	0	,
		0	,
		0	,
		0	)

gateway()

IPAddress gateway	(	0	,
		0	,
		0	,
		0	)

getCurrentTimeMessage()

Coap::Message getCurrentTimeMessage

(

)

Helper to build the time message.

ip()

IPAddress ip	(	192	,
		168	,
		0	,
		DEVICE_ID	)

loop()

void loop

(

)

sendNotification()

void sendNotification

(

)

setup()

void setup

(

)

subnet()

IPAddress subnet	(	255	,
		255	,
		255	,
		0	)

timeCallback()

void timeCallback	(	Coap::Message &	message,
		IPAddress	ip,
		uint16_t	port )

Declaration of our callback to liked to the "time" resource.

For the purpose of this example, our resource is simply millis().

Variable Documentation

coapNode

Coap::Node coapNode(Udp)

(

Udp

)

mac

byte mac[] = {0xBE, 0xEF, 0xBE, 0xEF, 0x00, DEVICE_ID}

myObservers

Coap::ObserverRegistry<5> myObservers

Udp

EthernetUDP Udp