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Clean up Redisson pub/sub listeners when assoicated object is 'stale'

I'm trying to implement a simple Websocket application in Java that is able to scale horizontally, by using Redis and the Redisson library.
The Websocket server basically keeps track of connected clients, and sends message that are received to an Rtopic - this works great.
To consume, I have code that adds a listener when a client is registered : it associated a Client object with a listener by:
private static RedissonClient redisson = RedissonRedisServer.createRedisConnectionWithConfig();
public static final RTopic subcriberTopic = redisson.getTopic("clientsMapTopic");
public static boolean sendToPubSub(ConnectedClient q, String message) {
boolean[] success = {true};
MessageListener<Message> listener = new MessageListener<Message>() {
#Override
public void onMessage(CharSequence channel, Message message) {
logger.debug("The message is : " + message.getMediaId());
try {
logger.debug("ConnectedClient mediaid: " + q.getMediaid() + ",Message mediaid " + message.getMediaId());
if (q.getMediaid().equals(message.getMediaId())) {
// we need to verify if the message goes to the right receiver
logger.debug("MESSAGE from PUBSUB to (" + q.getId() + ") # " + q.getSession().getId() + " " + message);
// this is the actual message to the websocket client
// this executes on the wrong connected client when the connection is closed and reopened
q.getSession().getBasicRemote().sendText(message.getMessage());
}
} catch (Exception e) {
e.printStackTrace();
success[0] = false;
}
}
};
int listenerId = subcriberTopic.addListener(Message.class, listener);
}
The problem I am observing is as follows:
initial connection from client registers listener associated with that object
sent message to the ws server gets picked up by listener and sent properly
disconnect websocket - create new connection - new listener gets created
sent message to the ws server gets picked up by same original listener and uses that connected client instead of the newly registered one
sending fails (because client and ws connection don't exist)and is not processes further
It seems I just need to remove the listener for the client if the client gets removed, but I haven't found a good way to do that because although I see in the debugger that the listener has the associated connected client object, I'm unable to retrieve them without adding code for that.
Am I observing this correctly and what is a good way to make this work properly?

When I was writing the question, I kind of leaned to an answer that I had in mind and tried, which worked.
I added a ConcurrentHashmap to keep track of the relation between the connected client and the listener.
In the logic where I handled websocket error that pointed to a client removing, I then removed the listener that was associated (and the entry from the map).
Now it works as expected.
small snippet:
int listenerId = subcriberTopic.addListener(Message.class, listener);
clientListeners.put(q,(Integer)listenerId);
And then in the websocket onError handler that triggers the cleanup:
// remove the associated listener
int listenerIdForClient = MessageContainer.clientListeners.get(cP);
MessageContainer.subcriberTopic.removeListener((Integer) listenerIdForClient);
// remove entry from map
MessageContainer.clientListeners.remove(cP);
Now the listener gets cleaned up properly and the next time a new listener gets created and handles the messages.

How To Detect An Email Address Is Real

IMPORTANT
I have been blocked by hotmail services. There is a control mechanism
called spamhaus which kicked me out. I'm stuck right now.
I am trying to detect an email address is valid and if its valid then check if this email address potentially used (I know that its not certain). For example, lets assume that there is a website with domain myimaginarydomain.com. If I run code below, I guess it won't fail because domain address is valid. But nobody can take an email address with that domain.
Is there any way to find out that email address is valid? (In this case its invalid)
I don't want to send confirmation email
Sending ping may be useful?
public class Application {
private static EmailValidator validator = EmailValidator.getInstance();
public static void main(String[] args) {
while (true) {
Scanner scn = new Scanner(System.in);
String email = scn.nextLine();
boolean isValid = validateEmail(email);
System.out.println("Syntax is : " + isValid);
if (isValid) {
String domain = email.split("#")[1];
try {
int test = doLookup(domain);
System.out.println(domain + " has " + test + " mail servers");
} catch (NamingException e) {
System.out.println(domain + " has 0 mail servers");
}
}
}
}
private static boolean validateEmail(String email) {
return validator.isValid(email);
}
static int doLookup(String hostName) throws NamingException {
Hashtable env = new Hashtable();
env.put("java.naming.factory.initial",
"com.sun.jndi.dns.DnsContextFactory");
DirContext ictx = new InitialDirContext(env);
Attributes attrs =
ictx.getAttributes(hostName, new String[]{"MX"});
Attribute attr = attrs.get("MX");
if (attr == null) return (0);
return (attr.size());
}
}

There is no failsafe way to do this in all cases, but, assuming the server uses SMTP then https://www.labnol.org/software/verify-email-address/18220/ gives quite a good tutorial on one method that may work.
The method used in the tutorial relies on OS tools, so you will need to ensure they exist before using them. a ProcessBuilder may help. Alternatively, you can open a socket directly in code and avoid using OS-dependent tools.
Essentially, you find out what the mail servers are (using nslookup), then telnet to one of the mail servers and start writing an email:
3a: Connect to the mail server:
telnet gmail-smtp-in.l.google.com 25
3b: Say hello to the other server
HELO
3c: Identify yourself with some fictitious email address
mail from:<labnol#labnol.org>
3d: Type the recipient’s email address that you are trying to verify:
rcpt to:<billgates#gmail.com>
The server response for rcpt to command will give you an idea whether an email address is valid or not. You’ll get an “OK” if the address exists else a 550 error

There really is no sensible way except trying to send a notification with a token to the address and ask the other party to confirm it, usually by visiting a web-page:
the recipients MX may be unavailable at the moment but come back online later, so you cannot rely on a lookup in real time;
just because the MX accepts the email doesn't mean that the address is valid, the message could bounce later down the pipe (think UUCP);
if this is some kind of registration service, you need to provide some confirmation step anyway as otherwise it'd become too easy to subscribe random strangers on the internet that do not want your service.

Plivo SMS is not being sent and getting error in Java

I am integrating Plivo SMS API with my java web application. I want to send messages through my application. I am referring to https://www.plivo.com/docs/getting-started/send-a-single-sms/ link.
Below is the code snippet:
String authId = "{my Auth_id}"; //Your Authentication ID
String authToken = "{my auth Token}"; //Your authentication code
RestAPI api = new RestAPI(authId, authToken, "v1");
LinkedHashMap<String, String> parameters = new LinkedHashMap<String, String>();
parameters.put("src", "+44*******"); // Sender's phone number with country code
parameters.put("dst", "+91*******"); // Receiver's phone number with country code
parameters.put("text", "Hi, text from Plivo"); // Your SMS text message
try {
// Send the message
MessageResponse msgResponse = api.sendMessage(parameters);
// Print the response
System.out.println(msgResponse);
// Print the Api ID
System.out.println("Api ID : " + msgResponse.apiId);
// Print the Response Message
System.out.println("Message : " + msgResponse.message);
if (msgResponse.serverCode == 202) {
// Print the Message UUID
System.out.println("Message UUID : " + msgResponse.messageUuids.get(0).toString());
} else {
System.out.println(msgResponse.error);
}
} catch (PlivoException e) {
System.out.println(e.getLocalizedMessage());
}
I tried to run this code using console application as well as web application.I am getting exception "com.plivo.helper.exception.PlivoException: Connection to https://api.plivo.com refused". What is wrong with my code? Am I missing anything here?

Plivo Sales Engineer here.
Please check your firewall settings to ensure that it's not blocking any traffic. Also, are you using a web proxy? If yes, make sure that your application is using this proxy to handle connections.

Accses to data from IoT Hub Azure with Java

I send data to the IoT Hub and receive it, it works, but i dont know how i can work with the received Data: here is my Code to receive data:
public void accept(PartitionReceiver receiver)
{
System.out.println("** Created receiver on partition " + partitionId);
try {
while (true) {
Iterable<EventData> receivedEvents = receiver.receive(10).get();
int batchSize = 0;
if (receivedEvents != null)
{
for(EventData receivedEvent: receivedEvents)
{
System.out.println(String.format("| Time: %s", receivedEvent.getSystemProperties().getEnqueuedTime()));
System.out.println(String.format("| Device ID: %s", receivedEvent.getProperties().get("iothub-connection-device-id")));
System.out.println(String.format("| Message Payload: %s", new String(receivedEvent.getBody(), Charset.defaultCharset())));
batchSize++;
}
}
}
}
catch (Exception e)
{
System.out.println("Failed to receive messages: " + e.getMessage());
}
}
I would like to work with the received data, here I become the data as JSON String:
System.out.println(String.format("| Message Payload: %s", new String(receivedEvent.getBody(), Charset.defaultCharset())));
The dataoutput is: product: xy, price: 2.3.
I would like take the data to :
String product= product;
double price= price;
How can I the received Payload save in the variable?
Thanks

There are two kinds of messages which include device-to-cloud and cloud-to-device.
For the first kind, device-to-cloud messages, as #DominicBetts said, you can refer to the section Receive device-to-cloud messages to know how to receive d2c messages with Event Hub-compatible endpoint. And there are two samples as references on GitHub, please see below.
Simple send/receive sample: Shows how to connect then send and receive messages to and from IoT Hub, passing the protocol of your choices as a parameter.
Simple sample handling messages received: : Shows how to connect to IoT Hub and manage messages received from IoT Hub, passing the protocol of your choices as a parameter.
For the second kind, cloud-to-device messages, you can refer to the section Receiving messages on the simulated device to know how to receive c2d messages. The sample code in the article was writen for C#, but I think it's simple for using Java instead of C#, please notice the note in the section for choosing the suitable protocol.

How to get a reference to a non default MIDI Sequencer?

I am building a Java application that programatically generates a MIDI Sequence that is then sent over the LoopBe Internal Midi Port so that I can use Ableton Live instruments for better sound playback quality.
Please correct me if I am wrong. What I need is to generate a Sequence, that will contain Tracks that will contains MidiEvents, that will contain MIDI messages with time information. That I think I got down.
The real problem is how to send it over the LoopBe MIDI Port. For that I supposedly need a Sequencer, but I don't know how I can get one rather than the default one, and I don't want that.
I guess a workaround would be to write the Sequence to a .mid file and then programatically play it back on the LoopBe Port.
So my question is: How can I obtain a non-default Sequencer?

You need method MidiSystem.getSequencer(boolean). When you call it with false parameter, it gives you unconnected sequencer.
Get Receiver instance from your target MIDI device and set it to sequencer with seq.getTransmitter().setReceiver(rec) call.
Example snippet:
MIDIDevice device = ... // obtain the MIDIDevice instance
Sequencer seq = MidiSystem.getSequencer(false);
Receiver rec = device.getReceiver();
seq.getTransmitter().setReceiver(rec)
For examples on Sequencer use, see tutorial on http://docs.oracle.com/javase/tutorial/sound/MIDI-seq-methods.html

For my own project I use LoopBe1 to send MIDI signals to REAPER.
Of course, LoopBe1 should already be installed.
In this example I iterate through the system's MIDI devices for the external MIDI port of LoopBe and then send the note C 10 times.
import javax.sound.midi.*;
public class Main {
public static void main(String[] args) throws MidiUnavailableException, InvalidMidiDataException, InterruptedException {
MidiDevice external;
MidiDevice.Info[] devices = MidiSystem.getMidiDeviceInfo();
//Iterate through the devices to get the External LoopBe MIDI port
for (MidiDevice.Info deviceInfo : devices) {
if(deviceInfo.getName().equals("LoopBe Internal MIDI")){
if(deviceInfo.getDescription().equals("External MIDI Port")){
external = MidiSystem.getMidiDevice(deviceInfo);
System.out.println("Device Name : " + deviceInfo.getName());
System.out.println("Device Description : " + deviceInfo.getDescription() + "\n");
external.open();
Receiver receiver = external.getReceiver();
ShortMessage message = new ShortMessage();
for (int i = 0; i < 10; i++) {
// Start playing the note Middle C (60),
// moderately loud (velocity = 93).
message.setMessage(ShortMessage.NOTE_ON, 0, 60, 93);
long timeStamp = -1;
receiver.send(message, timeStamp);
Thread.sleep(1000);
}
external.close();
}
}
}
}
}
For further information about the sending a MIDI signal, refer to this link:
https://docs.oracle.com/javase/tutorial/sound/MIDI-messages.html
I hope this helps!