I'm trying to figure out how to receive multiple messages in HiveMQ Client using the same try catch block even using different clients. I followed this example:
The above example works fine with one client and a single publish and subscribe but I'd like to perform multiple of these actions in the same block of the try catch if possible.
package com.main;
import java.util.UUID;
import com.hivemq.client.mqtt.MqttGlobalPublishFilter;
import com.hivemq.client.mqtt.datatypes.MqttQos;
import com.hivemq.client.mqtt.mqtt5.Mqtt5BlockingClient;
import com.hivemq.client.mqtt.mqtt5.Mqtt5BlockingClient.Mqtt5Publishes;
import com.hivemq.client.mqtt.mqtt5.Mqtt5Client;
import com.hivemq.client.mqtt.mqtt5.message.publish.Mqtt5Publish;
import java.util.logging.Logger;
import java.util.NoSuchElementException;
import java.util.logging.Level;
import java.util.concurrent.TimeUnit;
public class Main {
private static final Logger LOGGER = Logger.getLogger(Main.class.getName()); // Creates a logger instance
public static void main(String[] args) {
Mqtt5BlockingClient client1 = Mqtt5Client.builder()
.identifier(UUID.randomUUID().toString()) // the unique identifier of the MQTT client. The ID is randomly generated between
.serverHost("localhost") // the host name or IP address of the MQTT server. Kept it 0.0.0.0 for testing. localhost is default if not specified.
.serverPort(1883) // specifies the port of the server
.buildBlocking(); // creates the client builder
client1.connect(); // connects the client
System.out.println("Client1 Connected");
Mqtt5BlockingClient client2 = Mqtt5Client.builder()
.identifier(UUID.randomUUID().toString()) // the unique identifier of the MQTT client. The ID is randomly generated between
.serverHost("localhost") // the host name or IP address of the MQTT server. Kept it 0.0.0.0 for testing. localhost is default if not specified.
.serverPort(1883) // specifies the port of the server
.buildBlocking(); // creates the client builder
client2.connect(); // connects the client
System.out.println("Client2 Connected");
String testmessage = "How is it going!";
byte[] messagebytesend = testmessage.getBytes(); // stores a message as a byte array to be used in the payload
try {
Mqtt5Publishes publishes = client1.publishes(MqttGlobalPublishFilter.ALL); // creates a "publishes" instance thats used to queue incoming messages
// .ALL - filters all incoming Publish messages
client1.subscribeWith() // creates a subscription
.topicFilter("test/something1/topic") // filters to receive messages only on this topic (# = Multilevel wild card, + = single level wild card)
.qos(MqttQos.AT_LEAST_ONCE) // Sets the QoS to 2 (At least once)
.send();
System.out.println("The client1 has subscribed");
client1.publishWith() // publishes the message to the subscribed topic
.topic("test/something1/topic") // publishes to the specified topic
.qos(MqttQos.AT_LEAST_ONCE)
.payload(messagebytesend) // the contents of the message
.send();
System.out.println("The client1 has published");
Mqtt5Publish receivedMessage = publishes.receive(5,TimeUnit.SECONDS).get(); // receives the message using the "publishes" instance waiting up to 5 seconds // .get() returns the object if available or throws a NoSuchElementException
byte[] tempdata = receivedMessage.getPayloadAsBytes(); // converts the "Optional" type message to a byte array
System.out.println();
String getdata = new String(tempdata); // converts the byte array to a String
System.out.println(getdata);
client2.subscribeWith() // creates a subscription
.topicFilter("test/something2/topic") // filters to receive messages only on this topic (# = Multilevel wild card, + = single level wild card)
.qos(MqttQos.AT_LEAST_ONCE) // Sets the QoS to 2 (At least once)
.send();
System.out.println("The client2 has subscribed");
client2.publishWith() // publishes the message to the subscribed topic
.topic("test/something2/topic") // publishes to the specified topic
.qos(MqttQos.AT_LEAST_ONCE)
.payload("The second message :P".getBytes()) // the contents of the message
.send();
System.out.println("The client2 has published");
System.out.println();
// VV Why isn't the publish instance below receiving the second message? Do i need another try catch? VV
receivedMessage = publishes.receive(5,TimeUnit.SECONDS).get(); // receives the message using the "publishes" instance waiting up to 5 seconds // .get() returns the object if available or throws a NoSuchElementException
byte[] tempdata2 = receivedMessage.getPayloadAsBytes(); // converts the "Optional" type message to a byte array
System.out.println();
getdata = new String(tempdata2); // converts the byte array to a String
System.out.println(getdata);
}
catch (InterruptedException e) { // Catches interruptions in the thread
LOGGER.log(Level.SEVERE, "The thread was interrupted while waiting for a message to be received", e);
}
catch (NoSuchElementException e){
System.out.println("There are no received messages"); // Handles when a publish instance has no messages
}
client1.disconnect();
System.out.println("Client1 Disconnected");
client2.disconnect();
System.out.println("Client2 Disconnected");
}
}
The output I'm getting:
Client1 Connected
Client2 Connected
The client1 has subscribed
The client1 has published
How is it going!
The client2 has subscribed
The client2 has published
There are no received messages
Client1 Disconnected
Client2 Disconnected
The output I want:
Client1 Connected
Client2 Connected
The client1 has subscribed
The client1 has published
How is it going!
The client2 has subscribed
The client2 has published
The second message :P
Client1 Disconnected
Client2 Disconnected
