QCoapClient Class

The QCoapClient class allows the application to send CoAP requests and receive replies. More...

Header: #include <QCoapClient>
qmake: QT += coap
Inherits: QObject

Note: All functions in this class are reentrant.

Public Functions

QCoapClient(QtCoap::SecurityMode securityMode = QtCoap::SecurityMode::NoSecurity, QObject *parent = nullptr)
virtual ~QCoapClient()
void cancelObserve(QCoapReply *notifiedReply)
void cancelObserve(const QUrl &url)
QCoapReply *deleteResource(const QCoapRequest &request)
QCoapReply *deleteResource(const QUrl &url)
void disconnect()
QCoapResourceDiscoveryReply *discover(const QUrl &url, const QString &discoveryPath = QLatin1String("/.well-known/core"))
QCoapResourceDiscoveryReply *discover(QtCoap::MulticastGroup group = QtCoap::MulticastGroup::AllCoapNodesIPv4, int port = QtCoap::DefaultPort, const QString &discoveryPath = QLatin1String("/.well-known/core"))
QCoapReply *get(const QCoapRequest &request)
QCoapReply *get(const QUrl &url)
QCoapReply *observe(const QCoapRequest &request)
QCoapReply *observe(const QUrl &url)
QCoapReply *post(const QCoapRequest &request, const QByteArray &data = QByteArray())
QCoapReply *post(const QCoapRequest &request, QIODevice *device)
QCoapReply *post(const QUrl &url, const QByteArray &data = QByteArray())
QCoapReply *put(const QCoapRequest &request, const QByteArray &data = QByteArray())
QCoapReply *put(const QCoapRequest &request, QIODevice *device)
QCoapReply *put(const QUrl &url, const QByteArray &data = QByteArray())
void setAckRandomFactor(double ackRandomFactor)
void setAckTimeout(uint ackTimeout)
void setBlockSize(quint16 blockSize)
void setMaximumRetransmitCount(uint maximumRetransmitCount)
void setMaximumServerResponseDelay(uint responseDelay)
void setMinimumTokenSize(int tokenSize)
void setSecurityConfiguration(const QCoapSecurityConfiguration &configuration)
void setSocketOption(QAbstractSocket::SocketOption option, const QVariant &value)

Signals

void error(QCoapReply *reply, QtCoap::Error error)
void finished(QCoapReply *reply)
void responseToMulticastReceived(QCoapReply *reply, const QCoapMessage &message, const QHostAddress &sender)

Detailed Description

The QCoapClient class contains signals that get triggered when the reply of a sent request has arrived.

The application can use a QCoapClient to send requests over a CoAP network. It provides functions for standard requests: each returns a QCoapReply object, to which the response data shall be delivered; this can be read when the finished() signal arrives.

A simple request can be sent with:

QCoapClient *client = new QCoapClient(this);
connect(client, &QCoapClient::finished, this, &TestClass::slotFinished);
client->get(QCoapRequest(Qurl("coap://coap.me/test")));

Note: After processing of the request has finished, it is the responsibility of the user to delete the QCoapReply object at an appropriate time. Do not directly delete it inside the slot connected to finished(). You can use the deleteLater() function.

You can also use an observe request. This can be used as above, or more conveniently with the QCoapReply::notified() signal:

QCoapRequest request = QCoapRequest(Qurl("coap://coap.me/obs"));
QCoapReply *reply = client->observe(request);
connect(reply, &QCoapReply::notified, this, &TestClass::slotNotified);

And the observation can be cancelled with:

client->cancelObserve(reply);

When a reply arrives, the QCoapClient emits a finished() signal.

Note: For a discovery request, the returned object is a QCoapResourceDiscoveryReply. It can be used the same way as a QCoapReply but contains also a list of resources.

See also QCoapRequest, QCoapReply, and QCoapResourceDiscoveryReply.

Member Function Documentation

QCoapClient::QCoapClient(QtCoap::SecurityMode securityMode = QtCoap::SecurityMode::NoSecurity, QObject *parent = nullptr)

Constructs a QCoapClient object for the given securityMode and sets parent as the parent object.

The default for securityMode is QtCoap::NoSecurity, which disables security.

This connects using a QCoapQUdpConnection; to use a custom transport, sub-class QCoapConnection and pass an instance to one of the other constructors.

[signal] void QCoapClient::error(QCoapReply *reply, QtCoap::Error error)

This signal is emitted whenever an error occurs. The reply parameter can be nullptr if the error is not related to a specific QCoapReply. The error parameter contains the error code.

See also finished(), QCoapReply::error(), and QCoapReply::finished().

[signal] void QCoapClient::finished(QCoapReply *reply)

This signal is emitted along with the QCoapReply::finished() signal whenever a CoAP reply is received, after either a success or an error. The reply parameter will contain a pointer to the reply that has just been received.

See also error(), QCoapReply::finished(), and QCoapReply::error().

[signal] void QCoapClient::responseToMulticastReceived(QCoapReply *reply, const QCoapMessage &message, const QHostAddress &sender)

This signal is emitted when a unicast response to a multicast request arrives. The reply parameter contains a pointer to the reply that has just been received, message contains the payload and the message details, and sender contains the sender address.

See also error(), QCoapReply::finished(), and QCoapReply::error().

[virtual] QCoapClient::~QCoapClient()

Destroys the QCoapClient object and frees up any resources. Note that QCoapReply objects that are returned from this class have the QCoapClient set as their parents, which means that they will be deleted along with it.

void QCoapClient::cancelObserve(QCoapReply *notifiedReply)

This is an overloaded function.

Cancels the observation of a resource using the reply notifiedReply returned by the observe() method.

See also observe().

void QCoapClient::cancelObserve(const QUrl &url)

This is an overloaded function.

Cancels the observation of a resource identified by the url.

See also observe().

QCoapReply *QCoapClient::deleteResource(const QCoapRequest &request)

Sends the request using the DELETE method and returns a new QCoapReply object.

See also get(), put(), post(), observe(), and discover().

QCoapReply *QCoapClient::deleteResource(const QUrl &url)

This is an overloaded function.

Sends a DELETE request to the target url.

See also get(), put(), post(), observe(), and discover().

void QCoapClient::disconnect()

Closes the open sockets and connections to free the transport.

Note: In the secure mode this needs to be called before changing the security configuration or connecting to another server.

See also setSecurityConfiguration().

QCoapResourceDiscoveryReply *QCoapClient::discover(const QUrl &url, const QString &discoveryPath = QLatin1String("/.well-known/core"))

Discovers the resources available at the given url and returns a new QCoapResourceDiscoveryReply object which emits the QCoapResourceDiscoveryReply::discovered() signal whenever the response arrives.

Discovery path defaults to "/.well-known/core", but can be changed by passing a different path to discoveryPath. Discovery is described in RFC 6690.

See also get(), post(), put(), deleteResource(), and observe().

QCoapResourceDiscoveryReply *QCoapClient::discover(QtCoap::MulticastGroup group = QtCoap::MulticastGroup::AllCoapNodesIPv4, int port = QtCoap::DefaultPort, const QString &discoveryPath = QLatin1String("/.well-known/core"))

This is an overloaded function.

Discovers the resources available at the endpoints which have joined the group at the given port. Returns a new QCoapResourceDiscoveryReply object which emits the QCoapResourceDiscoveryReply::discovered() signal whenever a response arrives. The group is one of the CoAP multicast group addresses and defaults to QtCoap::AllCoapNodesIPv4.

Discovery path defaults to "/.well-known/core", but can be changed by passing a different path to discoveryPath. Discovery is described in RFC 6690.

See also get(), post(), put(), deleteResource(), and observe().

QCoapReply *QCoapClient::get(const QCoapRequest &request)

Sends the request using the GET method and returns a new QCoapReply object.

See also post(), put(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::get(const QUrl &url)

This is an overloaded function.

Sends a GET request to url and returns a new QCoapReply object.

See also post(), put(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::observe(const QCoapRequest &request)

Sends a request to observe the target request and returns a new QCoapReply object which emits the QCoapReply::notified() signal whenever a new notification arrives.

See also cancelObserve(), get(), post(), put(), deleteResource(), and discover().

QCoapReply *QCoapClient::observe(const QUrl &url)

This is an overloaded function.

Sends a request to observe the target url and returns a new QCoapReply object which emits the QCoapReply::notified() signal whenever a new notification arrives.

See also cancelObserve(), get(), post(), put(), deleteResource(), and discover().

QCoapReply *QCoapClient::post(const QCoapRequest &request, const QByteArray &data = QByteArray())

Sends the request using the POST method and returns a new QCoapReply object. Uses data as the payload for this request.

See also get(), put(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::post(const QCoapRequest &request, QIODevice *device)

This is an overloaded function.

Sends the request using the POST method and returns a new QCoapReply object. Uses device content as the payload for this request. A null device is treated as empty content.

Note: The device has to be open and readable before calling this function.

See also get(), put(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::post(const QUrl &url, const QByteArray &data = QByteArray())

This is an overloaded function.

Sends a POST request to url and returns a new QCoapReply object. Uses data as the payload for this request.

See also get(), put(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::put(const QCoapRequest &request, const QByteArray &data = QByteArray())

Sends the request using the PUT method and returns a new QCoapReply object. Uses data as the payload for this request.

See also get(), post(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::put(const QCoapRequest &request, QIODevice *device)

This is an overloaded function.

Sends the request using the PUT method and returns a new QCoapReply object. Uses device content as the payload for this request. A null device is treated as empty content.

Note: The device has to be open and readable before calling this function.

See also get(), post(), deleteResource(), observe(), and discover().

QCoapReply *QCoapClient::put(const QUrl &url, const QByteArray &data = QByteArray())

This is an overloaded function.

Sends a PUT request to url and returns a new QCoapReply object. Uses data as the payload for this request.

See also get(), post(), deleteResource(), observe(), and discover().

void QCoapClient::setAckRandomFactor(double ackRandomFactor)

Sets the ACK_RANDOM_FACTOR value defined in RFC 7252 - Section 4.2, to ackRandomFactor. This value should be greater than or equal to 1. The default is 1.5.

See also setAckTimeout().

void QCoapClient::setAckTimeout(uint ackTimeout)

Sets the ACK_TIMEOUT value defined in RFC 7252 - Section 4.2 to ackTimeout in milliseconds. The default is 2000 ms.

This timeout only applies to confirmable messages. The actual timeout for reliable transmissions is a random value between ACK_TIMEOUT and ACK_TIMEOUT * ACK_RANDOM_FACTOR.

See also setAckRandomFactor().

void QCoapClient::setBlockSize(quint16 blockSize)

Sets the maximum block size used by the protocol to blockSize when sending requests and receiving replies. The block size must be a power of two.

void QCoapClient::setMaximumRetransmitCount(uint maximumRetransmitCount)

Sets the MAX_RETRANSMIT value defined in RFC 7252 - Section 4.2 to maximumRetransmitCount. This value should be less than or equal to 25. The default is 4.

void QCoapClient::setMaximumServerResponseDelay(uint responseDelay)

Sets the MAX_SERVER_RESPONSE_DELAY value to responseDelay in milliseconds. The default is 250 seconds.

As defined in RFC 7390 - Section 2.5, MAX_SERVER_RESPONSE_DELAY is the expected maximum response delay over all servers that the client can send a multicast request to.

void QCoapClient::setMinimumTokenSize(int tokenSize)

Sets the minimum token size to tokenSize in bytes. For security reasons it is recommended to use tokens with a length of at least 4 bytes. The default value for this parameter is 4 bytes.

void QCoapClient::setSecurityConfiguration(const QCoapSecurityConfiguration &configuration)

Sets the security configuration parameters from configuration. Configuration will be ignored if the QtCoap::NoSecurity mode is used.

Note: This method must be called before the handshake starts. If you need to change the security configuration after establishing a secure connection with the server, the client needs to be disconnected first.

See also disconnect().

void QCoapClient::setSocketOption(QAbstractSocket::SocketOption option, const QVariant &value)

Sets the QUdpSocket socket option to value.

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