Fix message sending to cloud service

cloud/src/main/java/com/fogcomputing/CloudService.java

 package com.fogcomputing;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.TimeUnit;
 
+import org.zeromq.SocketType;
+import org.zeromq.ZMQ;
 import picocli.CommandLine;
 
 public class CloudService implements Callable<Void> {
@@ -11,12 +14,28 @@ public class CloudService implements Callable<Void> {
 
 	@Override
 	public Void call() throws Exception {
+		try (ZMQ.Socket responder = ZContextProvider.getInstance().createSocket(SocketType.REP)) {
+
+			boolean connected = false;
+			while (!connected) {
+				connected = responder.connect("tcp://localhost:%s".formatted(cloudServicePort));
+				System.out.printf("Was not able to init cloud service on port %s...%n", cloudServicePort);
+				ThreadUtils.sleep(5, TimeUnit.SECONDS);
+			}
+			System.out.printf("Cloud service listening on port %s...%n", cloudServicePort);
+
+			while (!Thread.currentThread().isInterrupted()) {
+				//  Wait for next request from client
+				String string = responder.recvStr(0);
+				System.out.printf("Received request: [%s]\n", string);
+				responder.send("OK");
+			}
+		}
 		return null;
 	}
 
-	public static void main(String[] args) {
+	public static void main (String[]args){
 		int exitCode = new CommandLine(new CloudService()).execute(args);
 		System.exit(exitCode);
 	}
-
 }

common/src/main/java/com/fogcomputing/SensorData.java

 package com.fogcomputing;
 
 
+import java.io.Serializable;
+
 public record SensorData(
 		int temperature,
 		int usage
-) {
+)
+		implements Serializable
+{
 	public SensorData(String temperature, String usage) {
-		 this(Integer.parseInt(temperature), Integer.parseInt(usage));
+		this(Integer.parseInt(temperature), Integer.parseInt(usage));
 	}
 
 	@Override

common/src/main/java/com/fogcomputing/SensorDataBatch.java

 package com.fogcomputing;
 
+import java.io.Serializable;
 import java.sql.Timestamp;
 import java.util.List;
 
@@ -7,7 +8,9 @@ public record SensorDataBatch(
 		List<SensorData> sensorData,
 		int size,
 		Timestamp timestamp
-) {
+)
+		implements Serializable
+{
 	public SensorDataBatch(List<SensorData> sensorData, Timestamp timestamp) {
 		this(sensorData, sensorData.size(), timestamp);
 	}

edge/src/main/java/com/fogcomputing/EdgeService.java

@@ -24,13 +24,17 @@ public class EdgeService implements Callable<Void> {
 	@Override
 	public Void call() throws Exception {
 
-		registerShutdownHook(); // close ZContext during shutdown
+		registerShutdownHook(ZContextProvider::close); // close ZContext during shutdown
 		ExecutorService executor = Executors.newFixedThreadPool(3); // assuming we need 3 threads in total
 		ConcurrentLinkedQueue<SensorData> messageBuffer = new ConcurrentLinkedQueue<>();
 
 		startSensordataCollector(messageBuffer, executor);
-		startMessageSender(messageBuffer, executor);
-//		startMessageReceiver(executor);
+
+		ZMQ.Socket messageSender = startMessageSender(messageBuffer, executor);
+		registerShutdownHook(messageSender::close);
+
+//		ZMQ.Socket messageReceiver = startMessageReceiver(executor);
+//		registerShutdownHook(messageReceiver::close);
 
 		latch.await(); // keep the main thread alive
 		return null;
@@ -41,32 +45,30 @@ public class EdgeService implements Callable<Void> {
 		executor.submit(sensorDataCollector);
 	}
 
-	private void startMessageSender(ConcurrentLinkedQueue<SensorData> messageBuffer, ExecutorService executor) {
-		try (ZMQ.Socket cloudSocket = ZContextProvider.getInstance().createSocket(SocketType.REQ))
-		{
-			boolean connected = false;
-			while (!connected) {
-				connected = cloudSocket.connect("tcp://%s".formatted(cloudServerAddress));
-				System.out.printf("Was not able to connect to cloud server on %s...%n", cloudServerAddress);
-				ThreadUtils.sleep(5, TimeUnit.SECONDS);
-			}
-			MessageSender messageSender = new MessageSender(messageBuffer, cloudSocket);
-			executor.submit(messageSender);
+	private ZMQ.Socket startMessageSender(ConcurrentLinkedQueue<SensorData> messageBuffer, ExecutorService executor) {
+		ZMQ.Socket cloudSocket = ZContextProvider.getInstance().createSocket(SocketType.REQ);
+		boolean connected = false;
+		while (!connected) {
+			connected = cloudSocket.connect("tcp://%s".formatted(cloudServerAddress));
+			System.out.printf("Was not able to connect to cloud server on %s...%n", cloudServerAddress);
+			ThreadUtils.sleep(5, TimeUnit.SECONDS);
 		}
+		MessageSender messageSender = new MessageSender(messageBuffer, cloudSocket);
+		executor.submit(messageSender);
+		return cloudSocket;
 	}
 
-	private void startMessageReceiver(ExecutorService executor) {
-		try (ZMQ.Socket cloudSocket = ZContextProvider.getInstance().createSocket(SocketType.REP))
-		{
-			boolean connected = false;
-			while (!connected) {
-				connected = cloudSocket.connect("tcp://localhost:%s".formatted(edgeServicePort));
-				System.out.println("Was not able to start message receiver on localhost port %s...");
-				ThreadUtils.sleep(5, TimeUnit.SECONDS);
-			}
-			MessageReceiver messageReceiver = new MessageReceiver(cloudSocket);
-			executor.submit(messageReceiver);
+	private ZMQ.Socket startMessageReceiver(ExecutorService executor) {
+		ZMQ.Socket cloudSocket = ZContextProvider.getInstance().createSocket(SocketType.REP);
+		boolean connected = false;
+		while (!connected) {
+			connected = cloudSocket.connect("tcp://localhost:%s".formatted(edgeServicePort));
+			System.out.println("Was not able to start message receiver on localhost port %s...");
+			ThreadUtils.sleep(5, TimeUnit.SECONDS);
 		}
+		MessageReceiver messageReceiver = new MessageReceiver(cloudSocket);
+		executor.submit(messageReceiver);
+		return cloudSocket;
 	}
 
 	public static void main(String[] args) {
@@ -74,8 +76,8 @@ public class EdgeService implements Callable<Void> {
 		System.exit(exitCode);
 	}
 
-	private static void registerShutdownHook() {
-		Thread printingHook = new Thread(ZContextProvider::close);
+	private static void registerShutdownHook(Runnable runnable) {
+		Thread printingHook = new Thread(runnable);
 		Runtime.getRuntime().addShutdownHook(printingHook);
 	}
 }

edge/src/main/java/com/fogcomputing/MessageSender.java

@@ -48,7 +48,7 @@ public class MessageSender implements Runnable {
 			Timestamp currentDateTime = new Timestamp(System.currentTimeMillis());
 			SensorDataBatch sensorDataBatch = new SensorDataBatch(batch, currentDateTime);
 			System.out.printf("Batch ready to sent: %s\n", sensorDataBatch);
-//			trySendToCloud(sensorDataBatch); // not tested yet
+			trySendToCloud(sensorDataBatch);
 
 			ThreadUtils.sleep(15, TimeUnit.SECONDS);
 		}