[proxy] try to contact again nodes when they go offline

proxy/src/netpp/Handler.java

@@ -2,7 +2,6 @@ package netpp;
 
 import java.io.ByteArrayInputStream;
 import java.io.InputStream;
-import java.net.URI;
 import java.util.Date;
 
 import javax.json.Json;
@@ -15,19 +14,20 @@ import org.eclipse.californium.core.CoapResponse;
 
 public class Handler implements CoapHandler {
 	
-	private URI uri;
-	private Resource resource;
+	private Node node;
 	
-	public Handler(URI uri, Resource resource) {
-		this.uri = uri;
-		this.resource = resource;
-		System.err.println("[D] new handler for " + this.uri);
+	public Handler(Node node) {
+		this.node = node;
+		node.setStatus(Status.WAIT);
+		System.err.println("[D] new handler for " + this.node.getURI());
 	}
 
 	@Override
 	public void onLoad(CoapResponse response) {
 		String content = response.getResponseText();
-		System.out.println("[D] from " + this.uri + " update received at " + new Date() + " > " + content);
+		System.out.println("[D] from " + this.node.getURI() + " update received at " + new Date() + " > " + content);
+		
+		this.node.setStatus(Status.ONLINE);
 		
 		JsonArray jsonSenML = null;
 		try {
@@ -41,8 +41,8 @@ public class Handler implements CoapHandler {
 			String res_name = res.getString("n");	// name of resource
 			int res_value = res.getJsonNumber("v").intValue();	// value of resource
 
-			resource.setName(res_name);
-			resource.setValue(res_value);
+			this.node.getResource().setName(res_name);
+			this.node.getResource().setValue(res_value);
 		} catch (Exception ex) {
 			ex.printStackTrace();
 			System.err.println("[E] " + ex);
@@ -51,7 +51,8 @@ public class Handler implements CoapHandler {
 
 	@Override
 	public void onError() {
-		System.err.println("[E] failed " + uri);
+		node.setStatus(Status.OFFLINE);
+		System.err.println("[E] failed " + this.node.getURI());
 	}
 
 }

proxy/src/netpp/Main.java

@@ -25,6 +25,11 @@ public class Main {
 		final String prefix = args[0];
 		final int n = Integer.parseInt(args[1]);
 		
+		/* run server */
+		CoapServer server = new CoapServer();
+		server.start();
+		System.err.println("[D] server started");
+		
 		/* subscribe to every node specified */
 		System.err.println("[I] now subscribing to node [2; " + n + "] in " + prefix + "/64");
 		
@@ -33,27 +38,40 @@ public class Main {
 		for (int i = 2; i <= n; i++) {	// node 1 is the gateway, skip. And mind the <=
 			String uri_string = "coap://[" + prefix + ":" + COOJA_MAGIC + "::" + Integer.toString(i, 16) + "]" + resource;
 			System.err.println("[I] subscribing to " + uri_string);
-			nodeList.add(new Node(i, uri_string));
-		}
-		
-		/* run server */
-		CoapServer server = new CoapServer();
-		for (Node node : nodeList) {
+			
+			Node node = new Node(i, uri_string);
+			nodeList.add(node);
 			server.add(node.getResource());
 		}
-		server.start();
-		System.err.println("[D] server started");		
 		
-		/* thread sleep */
-		try {
-			Thread.sleep(5 * 60 * 1000);	// 5 min
-		} catch (InterruptedException ex) {
-			System.err.println(ex);
-		}
-		
-		/* shutting down everything */
-		for (Node node : nodeList) {
-			node.finalize();
+		/* periodically check for offline nodes */
+		while (true) {
+			System.err.println("[D] check for offline nodes...");
+			Node offline_node = null;
+			
+			for (Node node : nodeList) {
+				if (node.getStatus() == Status.OFFLINE) {
+					System.err.println("[I] detected offline node");
+					offline_node = node;
+					break;
+				}
+			}
+			
+			if (offline_node != null) {
+				System.err.println("[I] tryng again to contact " + offline_node.getURI());
+				nodeList.remove(offline_node);
+				server.remove(offline_node.getResource());
+				
+				Node new_node = new Node(0, offline_node.getURI().toString());
+				nodeList.add(new_node);
+				server.add(new_node.getResource());
+			}
+			/* thread sleep */
+			try {
+				Thread.sleep(5 * 1000);	// 5 sec
+			} catch (InterruptedException ex) {
+				System.err.println(ex);
+			}
 		}
 		
 	}

proxy/src/netpp/Node.java

@@ -5,7 +5,8 @@ import java.net.URISyntaxException;
 
 import org.eclipse.californium.core.CoapClient;
 import org.eclipse.californium.core.CoapObserveRelation;
-import org.eclipse.californium.core.CoapResource;
+
+enum Status { OFFLINE, WAIT, ONLINE };
 
 public class Node {
 	private URI uri;
@@ -14,6 +15,7 @@ public class Node {
 	private CoapObserveRelation relation;
 	private Handler handler;
 	Resource resource;
+	Status status = Status.OFFLINE;
 	
 	public Node(int quickname, String uriString) {
 		try {
@@ -21,7 +23,7 @@ public class Node {
 			this.client = new CoapClient(uri);
 			this.quickname = quickname;
 			this.resource = new Resource(this.quickname); /* this name will be overwritten when an update is received */
-			this.handler = new Handler(this.uri, resource);
+			this.handler = new Handler(this);
 			this.relation = client.observe(handler);
 		} catch (URISyntaxException e) {
 			System.err.println("[F] Invalid URI: " + e.getMessage());
@@ -29,10 +31,20 @@ public class Node {
 		}
 	}
 	
-	CoapResource getResource() {
+	Resource getResource() {
 		return this.resource;
 	}
 	
+	URI getURI() {
+		return this.uri;
+	}
+	Status getStatus() {
+		return this.status;
+	}
+	void setStatus(Status status) {
+		this.status = status;
+	}
+	
 	/* be kind with the poor resource constrained node */
 	@Override
 	public void finalize() {

proxy/src/netpp/Resource.java

@@ -15,12 +15,11 @@ public class Resource extends CoapResource {
 
 	public Resource(int quickname) {
 		super(Integer.toString(quickname, 16));
-		// setObservable(true); // TODO -- do we need to make this observable?
 		System.err.println("[D] resource created: " + super.getName());
 	}
 	
 	public void handleGET(CoapExchange exchange) {
-		// TODO build the proper JSON object
+		/* an RFC8428 (SenML) compliant JSON */
 		JsonArray senml = Json.createArrayBuilder()
 			.add(
 				Json.createObjectBuilder()