libcoap example client

coap-get.cpp

// g++ -o coap-get coap-get.cpp -lcoap-2-openssl -lPocoNet -lPocoFoundation


#include <Poco/Net/SocketAddress.h>
#include <Poco/Exception.h>
#include <coap2/coap.h>
#include <cstring>
#include <iostream>


int main(int argc, char** argv)
{
	coap_context_t* pCoapContext = nullptr;
	coap_session_t* pCoapSession = nullptr;

	coap_startup();

	try
	{
		Poco::Net::SocketAddress sockAddr("localhost", "5683");
		coap_address_t coapAddr;
		coapAddr.size = sockAddr.length();
		std::memcpy(&coapAddr.addr.sin, sockAddr.addr(), sockAddr.length());

		pCoapContext = coap_new_context(nullptr);
		if (!pCoapContext) throw Poco::IOException("cannot create CoAP context");

		pCoapSession = coap_new_client_session(pCoapContext, nullptr, &coapAddr, COAP_PROTO_UDP);
		if (!pCoapSession) throw Poco::IOException("cannot create CoAP client session");

		coap_register_response_handler(pCoapContext,
			[](coap_context_t* pCtx, coap_session_t* pSess, coap_pdu_t* pSent, coap_pdu_t* pReceived, const coap_tid_t id)
			{
				coap_show_pdu(LOG_WARNING, pReceived);
				std::size_t len;
				std::uint8_t* pData;
				coap_get_data(pReceived, &len, &pData);
				std::string data(reinterpret_cast<char*>(pData), len);
				std::cout << data << std::endl;
			}
		);

		coap_pdu_t* pRequestPDU = coap_pdu_init(
			COAP_MESSAGE_CON,
			COAP_REQUEST_GET,
			coap_new_message_id(pCoapSession),
			coap_session_max_pdu_size(pCoapSession)
		);
		if (!pRequestPDU) throw Poco::IOException("canot create PDU");

		std::string path("rssi");
		coap_add_option(pRequestPDU, COAP_OPTION_URI_PATH, path.size(), reinterpret_cast<const uint8_t*>(path.data()));

		coap_show_pdu(LOG_WARNING, pRequestPDU);

		coap_send(pCoapSession, pRequestPDU);

		coap_run_once(pCoapContext, 0);

	}
	catch (Poco::Exception& exc)
	{
		std::cerr << exc.displayText() << std::endl;
	}

	if (pCoapSession) coap_session_release(pCoapSession);
	if (pCoapContext) coap_free_context(pCoapContext);

	coap_cleanup();

	return 0;
}