Simple MQTT Client Example¶
The Simple MQTT Client example demonstrates how to create a minimal client application.
To use the application, you first specify a broker, such as
test.mosquitto.org or broker.hivemq.com and the port number 1883, and
connect to it. You can then subscribe to a topic and send a message, which
you will also receive.
Note
Port number 1883 is not encrypted, and therefore it is suitable only for development and testing purposes. In production, always use encrypted connections.
# Copyright (C) 2020 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
import sys
from PySide6.QtWidgets import QApplication
from mainwindow import MainWindow
if __name__ == "__main__":
app = QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec())
# Copyright (C) 2020 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from PySide6.QtCore import QByteArray, QDateTime, Slot
from PySide6.QtGui import QKeySequence
from PySide6.QtMqtt import QMqttClient, QMqttTopicName
from PySide6.QtWidgets import QMainWindow, QMessageBox
from ui_mainwindow import Ui_MainWindow as ui
class MainWindow(QMainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
self._ui = ui()
self._ui.setupUi(self)
self._ui.actionQuit.setShortcut(QKeySequence.StandardKey.Quit)
self._ui.actionQuit.triggered.connect(self.close)
self._client = QMqttClient(self)
self._client.setHostname(self._ui.lineEditHost.text())
self._client.setPort(self._ui.spinBoxPort.value())
self._client.stateChanged.connect(self.updateLogStateChange)
self._client.disconnected.connect(self.brokerDisconnected)
self._client.messageReceived.connect(self.on_messageReceived)
self._client.pingResponseReceived.connect(self.on_pingResponseReceived)
self._ui.lineEditHost.textChanged.connect(self._client.setHostname)
self._ui.spinBoxPort.valueChanged[int].connect(self.setClientPort)
self.updateLogStateChange()
@Slot()
def on_pingResponseReceived(self):
current_date = QDateTime.currentDateTime().toString()
self._ui.editLog.insertPlainText(current_date + "PingResponse\n")
@Slot(QByteArray, QMqttTopicName)
def on_messageReceived(self, message, topic):
current_date = QDateTime.currentDateTime().toString()
data = message.data().decode("utf-8")
content = f"{current_date} Received Topic: {topic.name()} Message: {data}\n"
self._ui.editLog.insertPlainText(content)
@Slot(int)
def setClientPort(self, p):
self._client.setPort(p)
@Slot()
def on_buttonConnect_clicked(self):
if self._client.state() == QMqttClient.Connected:
self._ui.lineEditHost.setEnabled(True)
self._ui.spinBoxPort.setEnabled(True)
self._ui.buttonConnect.setText("Connect")
self._client.disconnectFromHost()
elif self._client.hostname():
self._ui.lineEditHost.setEnabled(False)
self._ui.spinBoxPort.setEnabled(False)
self._ui.buttonConnect.setText("Disconnect")
self._client.connectToHost()
@Slot()
def on_buttonQuit_clicked(self):
qApp.quit() # noqa: F821
@Slot()
def updateLogStateChange(self):
current_date = QDateTime.currentDateTime().toString()
content = f"{current_date}: State Change {self._client.state()}\n"
self._ui.editLog.insertPlainText(content)
@Slot()
def brokerDisconnected(self):
self._ui.lineEditHost.setEnabled(True)
self._ui.spinBoxPort.setEnabled(True)
self._ui.buttonConnect.setText("Connect")
@Slot()
def on_buttonPublish_clicked(self):
topic = QMqttTopicName(self._ui.lineEditTopic.text())
message = QByteArray(self._ui.lineEditMessage.text().encode("utf-8"))
if self._client.publish(topic, message) == -1:
QMessageBox.critical(self, "Error", "Could not publish message")
@Slot()
def on_buttonSubscribe_clicked(self):
subscription = self._client.subscribe(self._ui.lineEditTopic.text())
if not subscription:
QMessageBox.critical(self, "Error",
"Could not subscribe. Is there a valid connection?")
return
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>1024</width>
<height>768</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<layout class="QVBoxLayout" name="verticalLayout">
<item>
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<layout class="QFormLayout" name="formLayout">
<item row="0" column="0">
<widget class="QLabel" name="label">
<property name="text">
<string>Host:</string>
</property>
</widget>
</item>
<item row="0" column="1">
<widget class="QLineEdit" name="lineEditHost">
<property name="text">
<string/>
</property>
</widget>
</item>
<item row="2" column="0">
<widget class="QLabel" name="label_2">
<property name="text">
<string>Port:</string>
</property>
</widget>
</item>
<item row="2" column="1">
<widget class="QSpinBox" name="spinBoxPort">
<property name="maximum">
<number>99999</number>
</property>
<property name="value">
<number>1883</number>
</property>
</widget>
</item>
</layout>
</item>
<item>
<widget class="QPushButton" name="buttonConnect">
<property name="text">
<string>Connect</string>
</property>
</widget>
</item>
</layout>
</item>
<item>
<layout class="QGridLayout" name="gridLayout">
<item row="1" column="1">
<widget class="QLineEdit" name="lineEditMessage">
<property name="text">
<string>This is a test message</string>
</property>
</widget>
</item>
<item row="1" column="0">
<widget class="QLabel" name="label_4">
<property name="text">
<string>Message:</string>
</property>
</widget>
</item>
<item row="0" column="2">
<widget class="QPushButton" name="buttonSubscribe">
<property name="text">
<string>Subscribe</string>
</property>
</widget>
</item>
<item row="1" column="2">
<widget class="QPushButton" name="buttonPublish">
<property name="text">
<string>Publish</string>
</property>
</widget>
</item>
<item row="0" column="1">
<widget class="QLineEdit" name="lineEditTopic">
<property name="text">
<string>qtmqtt/topic1</string>
</property>
</widget>
</item>
<item row="0" column="0">
<widget class="QLabel" name="label_3">
<property name="text">
<string>Topic:</string>
</property>
</widget>
</item>
</layout>
</item>
<item>
<widget class="QGroupBox" name="groupBox">
<property name="title">
<string>Log Messages</string>
</property>
<layout class="QHBoxLayout" name="horizontalLayout_2">
<item>
<widget class="QPlainTextEdit" name="editLog"/>
</item>
</layout>
</widget>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_3">
<item>
<spacer name="horizontalSpacer">
<property name="orientation">
<enum>Qt::Horizontal</enum>
</property>
<property name="sizeHint" stdset="0">
<size>
<width>40</width>
<height>20</height>
</size>
</property>
</spacer>
</item>
<item>
<widget class="QPushButton" name="buttonQuit">
<property name="text">
<string>Quit</string>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>1024</width>
<height>20</height>
</rect>
</property>
<widget class="QMenu" name="menuFile">
<property name="title">
<string>File</string>
</property>
<addaction name="actionQuit"/>
</widget>
<addaction name="menuFile"/>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
<action name="actionQuit">
<property name="text">
<string>Quit</string>
</property>
</action>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>