Hi i am very new to MQTT and I have made a 2 MQTT client jar files , one that publishers to a topic (it takes 3 args , "topic" , "message" , "host address of broker"), and another that subscribes to a topic (takes 2 args "topic","host address of broker"). the clients both work fine when sending normal plain text messages. however i am required to implement a simple gzip compression of the payload, on both the publisher and the subscriber client. The publisher successfully compresses the payload and sends it off however i am running into a problem when i try add decompression of the payload to the client , in as far as it its the decompression method and does not go any further. I a aware that some parts of the code are inefficient however i am just looking for a answer to the decompression problem.
Publisher client code:
package com;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Scanner;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
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.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class PahoDemo implements MqttCallback {
MqttClient client;
static String clientMessage="";
static String topic="";
static String ipAddress="";
static Scanner scan = new Scanner(System.in);
static byte[] compressedMessage;
public PahoDemo() {
}
public static byte[] compress(String data) throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length());
GZIPOutputStream gzip = new GZIPOutputStream(bos);
gzip.write(data.getBytes());
gzip.close();
byte[] compressed = bos.toByteArray();
bos.close();
return compressed;
}
public static String decompress(byte[] compressed) throws IOException {
ByteArrayInputStream bis = new ByteArrayInputStream(compressed);
GZIPInputStream gis = new GZIPInputStream(bis);
BufferedReader br = new BufferedReader(new InputStreamReader(gis, "UTF-8"));
StringBuilder sb = new StringBuilder();
String line;
while((line = br.readLine()) != null) {
sb.append(line);
}
br.close();
gis.close();
bis.close();
return sb.toString();
}
public static void main(String[] args) throws IOException {
new PahoDemo().setDetails(args[0], args[1],args[2]);
new PahoDemo().TestPahoClientPub();
}
public void setDetails(String topic,String message,String ipAddressEntered){
PahoDemo.topic=topic;
PahoDemo.clientMessage=message;
PahoDemo.ipAddress="tcp://"+ipAddressEntered+":1883";
}
public void TestPahoClientPub() throws IOException{
System.out.println("test pub ");
try {
MqttClient client = new MqttClient(ipAddress, "publisher");
client.connect();
MqttMessage message = new MqttMessage();
compressedMessage = PahoDemo.compress(clientMessage);
clientMessage = compressedMessage.toString();
message.setPayload(clientMessage.getBytes(Charset.forName("UTF-8")));
client.publish(topic, message);
client.disconnect();
} catch (MqttException e) {
e.printStackTrace();
}
}
public void doDemo() {
System.out.println("test sub");
try {
client = new MqttClient(ipAddress, "Subscriber");
client.connect();
client.setCallback(this);
client.subscribe(topic);
} catch (MqttException e) {
e.printStackTrace();
}
}
Subscriber client code:
package com;
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;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
import org.apache.commons.compress.utils.IOUtils;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
class SimpleCallback implements MqttCallback {
public static byte[] compress(String data) throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length());
GZIPOutputStream gzip = new GZIPOutputStream(bos);
gzip.write(data.getBytes());
gzip.close();
byte[] compressed = bos.toByteArray();
bos.close();
return compressed;
}
public static String decompress(final byte[] compressed) throws IOException {
ByteArrayInputStream bis = new ByteArrayInputStream(compressed);
GZIPInputStream gis = new GZIPInputStream(bis);
byte[] bytes = IOUtils.toByteArray(gis);
return new String(bytes, "UTF-8");
}
public static String decompressArrived(MqttMessage message) throws IOException{
byte[] messagePayload = message.getPayload();
String messageDecompressed = decompress(messagePayload).toString();
return messageDecompressed;
}
@Override
public void connectionLost(Throwable cause) { //Called when the client lost the connection to the broker
}
@Override
public void messageArrived(String topic, MqttMessage message) throws Exception {
System.out.println("-------------------------------------------------");
System.out.println("| Topic:" + topic);
System.out.println("| Message: " + new String(SimpleCallback.decompressArrived(message))); // here is the problem where the code stops
System.out.println("-------------------------------------------------");
}
@Override
public void deliveryComplete(IMqttDeliveryToken token) {//Called when a outgoing publish is complete
System.out.println("delivery complete");
}
}
public class MqttPublishSubscribeSample {
public static void main(String[] args){
String topic = args[0]; // topic name
String content = "Message from MqttPublishSample"; //payload of message
int qos = 2;
String broker = "tcp://"+args[1]+":1883";
String clientId = "JavaSample";
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);
sampleClient.subscribe("#", 1);
System.out.println("Connected");
System.out.println("Publish message: " + content);
MqttMessage message = new MqttMessage(content.getBytes());
message.setQos(qos);
sampleClient.setCallback(new SimpleCallback());
sampleClient.publish(topic, message); // just a test packet
System.out.println("Message published");
try {
Thread.sleep(5000);
} catch(Exception e) {
e.printStackTrace();
}
} 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("except " + me);
me.printStackTrace();
}
}
}
basically is there any modifications i can make to the messageArrived method in the subscriber client to allow it to print out the decompressed file.
Thanks.
