Pular para o conteúdo principal

Java MQTT Client with Eclipse Paho

This is a quick post to share a sample code using Eclipse Paho for MQTT.

Recommended: First steps with MQTT using Mosquitto

Some may prefer to use REST  or Websockets, but MQTT is the standard protocol to connect things to the Internet. Even a small NodeMCU can read and publish on MQTT topics. You can configure a RaspberryPi instance to be a mqtt server or even use a cloud MQTT server, such as Paho, Mosquitto and other servers on the cloud. There are also paid services such as Amazon AWS.
 
Here' s a very simple code to say hello from a Java application.


package org.fxapps.iot;
import java.util.Date;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
public class MqttPublish {
public static void main(String[] args) {
String topic = "fxapps/iot/test";
String content = "Hello World from Java: " + new Date();
int qos = 2;
String broker = "tcp://iot.eclipse.org:1883";
String clientId = "FXappsTest";
MemoryPersistence persistence = new MemoryPersistence();
try {
MqttClient sampleClient = new MqttClient(broker, clientId, persistence);
MqttConnectOptions connOpts = new MqttConnectOptions();
connOpts.setCleanSession(true);
System.out.println("Connecting to broker: " + broker);
sampleClient.connect(connOpts);
System.out.println("Connected");
System.out.println("Publishing message: " + content);
MqttMessage message = new MqttMessage(content.getBytes());
message.setQos(qos);
sampleClient.publish(topic, message);
System.out.println("Message published");
sampleClient.disconnect();
System.out.println("Disconnected");
System.exit(0);
} catch (MqttException me) {
System.out.println("reason " + me.getReasonCode());
System.out.println("msg " + me.getMessage());
System.out.println("loc " + me.getLocalizedMessage());
System.out.println("cause " + me.getCause());
System.out.println("excep " + me);
me.printStackTrace();
}
}
}
view raw MqttPublish.java hosted with ❤ by GitHub
package org.fxapps.iot;
import java.util.Scanner;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class MqttSubscribe implements MqttCallback {
String topic = "fxapps/iot/test";
String broker = "tcp://iot.eclipse.org:1883";
String clientId = "FXappsTest";
public static void main(String[] args) {
new MqttSubscribe();
}
public MqttSubscribe() {
try {
MqttClient sampleClient = new MqttClient(broker, clientId);
MqttConnectOptions connOpts = new MqttConnectOptions();
connOpts.setCleanSession(true);
System.out.println("Connecting to broker: " + broker);
sampleClient.connect(connOpts);
System.out.println("Connected");
System.out.println("Listening topic: " + topic);
sampleClient.subscribe(topic);
sampleClient.setCallback(this);
Scanner sc = new Scanner(System.in);
sc.nextLine();
sc.close();
sampleClient.disconnect();
} catch (MqttException me) {
me.printStackTrace();
}
}
@Override
public void connectionLost(Throwable cause) {
System.out.println(" Connection Lost!");
cause.printStackTrace();
}
@Override
public void messageArrived(String topic, MqttMessage message) throws Exception {
System.out.println("Message to topic " + topic + ": " + new String(message.getPayload()));
}
@Override
public void deliveryComplete(IMqttDeliveryToken token) {
}
}
view raw MqttSubscribe.java hosted with ❤ by GitHub
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.fxapps.iot</groupId>
<artifactId>mqtt-test</artifactId>
<version>1.0</version>
<dependencies>
<dependency>
<groupId>org.eclipse.paho</groupId>
<artifactId>org.eclipse.paho.client.mqttv3</artifactId>
<version>1.0.2</version>
</dependency>
</dependencies>
</project>
view raw pom.xml hosted with ❤ by GitHub

Marcadores

Marcadores:

Comentários

Postar um comentário

Postagens mais visitadas deste blog

Dancing lights with Arduino - The idea

I have been having fun with Arduino these days! In this article I am going to show how did I use an electret mic with Arduino to create a Dancing Lights circuit. Dancing Lights   I used to be an eletronician before starting the IT college. I had my own electronics maintenance office to fix television, radios, etc. In my free time I used to create electronic projects to sell and I made a few "reais" selling a version of Dancing lights, but it was too limited: it simply animated lamps using a relay in the output of a 4017 CMOS IC. The circuit was a decimal counter  controlled by a 555. 4017 decimal counter. Source in the image When I met Arduino a few years ago, I was skeptical because I said: I can do this with IC, why should I use a microcontroller. I thought that Arduino was for kids. But now my pride is gone and I am having a lot of fun with Arduino :-) The implementation of Dancing Lights with Arduino uses an electret mic to capture the sound and light leds...
Postar um comentário
Leia mais

Simplest JavaFX ComboBox autocomplete

Based on this Brazilian community post , I've created a sample Combobox auto complete. What it basically does is: When user type with the combobox selected, it will work on a temporary string to store the typed text; Each key typed leads to the combobox to be showed and updated If backspace is type, we update the filter Each key typed shows the combo box items, when the combobox is hidden, the filter is cleaned and the tooltip is hidden:   The class code and a sample application is below. I also added the source to my personal github , sent me PR to improve it and there are a lot of things to improve, like space and accents support.
2 comentários
Leia mais

Genetic algorithms with Java

One of the most fascinating topics in computer science world is Artificial Intelligence . A subset of Artificial intelligence are the algorithms that were created inspired in the nature. In this group, we have Genetic Algorithms  (GA). Genetic Algorithms  To find out more about this topic I recommend the following MIT lecture and the Nature of Code book and videos created by Daniel Shiffman. Genetic Algorithms using Java After I remembered the basics about it, I wanted to practice, so I tried my own implementation, but I would have to write a lot of code to do what certainly others already did. So I started looking for Genetic Algorithm libraries and found Jenetics , which is a modern library that uses Java 8 concepts and APIs, and there's also JGAP . I decided to use Jenetics because the User Guide was so clear and it has no other dependency, but Java 8. The only thing I missed for Jenetics are more small examples like the ones I will show i...
Postar um comentário
Leia mais