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# Tutorial for jCoAP Hands-on
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In this tutorial we will describe how to develop a simple message exchange between devices using jCoAP.
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Furthermore, we will introduce the observe mechanism.
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The following points will be covered by this tutorial:
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1. Installation of Copper Plugin for Mozilla Firefox
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2. Introduction of jCoAP (based on Task 1)
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3. Import of prepared project into Eclipse
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4. Task 1: Implementation of client/server and enable simple message exchange
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5. Task 2: Implementation of an airconditioner control by using the CoAP-observe mechanism
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## 0. The requirements for this tutorial:
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* JAVA SE JDK 1.6+
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* Eclipse IDE for JAVA development
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* Prepared JAVA project files for Hands-on
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* (Copper plugin for Mozilla Firefox)
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## 1. Installation of Copper Plugin for Mozilla Firefox
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- https://addons.mozilla.org/de/firefox/addon/copper-270430/
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- Click on „add to Firefox“ & Confirm Installation
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- Restart Firefox
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## 2. Introduction of jCoAP
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- WS4D-jCoAP: Java implementation of CoAP
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- http://ws4d.org/
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- https://gitlab.amd.e-technik.uni-rostock.de/ws4d/jcoap
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### Task 1 – Sequence Diagram
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Server Side
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Client Side
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- Server:
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- individual implementation of a server application, creates CoapResourceServer and resources
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- TemperatureResource:
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- individual resource, inherits from BasicCoapResource
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- BasicCoapResource:
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- already implemented resource with basic functionality, implements CoapResource (interface)
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- CoapResource (interface):
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- describes interfaces that must be supported by each resource.
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- CoapResourceServer:
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- manages a list of resources, enables access of these resources from outside, implements
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- CoapServer (interface):
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- uses ChannelManager for connection management.
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- CoapServer (interface):
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- describes interfaces that must be supported by a resource server
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- ChannelManager:
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- manages channels
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- Channel:
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- one channel represents a connection to one client
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- Client:
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- individual implementation of a client application, implements CoapClient (interface)
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- CoapClient (interface):
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- describes interfaces that must be supported by a client
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* ToDo on server side:
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1. Create a new resource class TemperatureResource
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2. Instantiate a new ResourceServer
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3. Instantiate a new TemperatureResource
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4. Add the TemperatureResource to the ResourceServer
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5. Run the ResourceServer
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* ToDo on client side:
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1. Establish a connection to the Server using the ChannelManager
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2. Create a CoapRequest & add some Options
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3. Send the CoapRequest
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4. Wait for CoapResponse
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5. Print the CoapResponse on the console
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## 3. Import of prepared project into Eclipse
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1. File > Import
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2. General > Existing Projects ...
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3. Click ‚Next‘
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4. Browse <Select Project Folder>
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5. Click ‚Finish’
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* the resulting GUI should look like this:
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* We have prepared some FIXME and TODO annotations:
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* Just open the „Task“ view
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* FIXMEs are for the first task (message exchange)
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* TODOs are for the second task (observe and AC control)
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* If you do not have a „Task“ view:
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* Window > Show View > Other
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* Type „task“
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* Select „General > Task“ view
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## 4. Task 1: Implementation of client/server and enable simple message exchange
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1. Create a new resource class TemperatureResource (already done in our example Server)
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2. Instantiate a new ResourceServer
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3. Instantiate a new TemperatureResource
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4. Add the TemperatureResource to the ResourceServer
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5. Run the ResourceServer
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1. Create a new resource class TemperatureResource (TemperatureResource.java):
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* We could have used the predefined BasicCoapResource
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* BasicCoapResource is a resource that just keeps a static `byte[ ]` that is:
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* returned on GET requests
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* replaced by the payload on PUT requests
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* appended with the payload on POST requests
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* deleted on DELETE requests
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* We do not want a static `byte[ ]`
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* Instead we want a random number to be returned on a GET
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* PUT, POST and DELETE are not used
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* ->So we implemented TemperatureResource wich extends BasicCoapResource with:
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* A constructor
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* To initialize the resource
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* Disallow POST, PUT and DELETE
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* 2 get() Methods
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* Get a list of accepted media types [& query parameters]
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* Returns a `byte[ ]` together with its media type
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* And the `getResourceType()` method
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* Wich returns a description string of the resource
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2. Instantiate a new ResourceServer (Server.java, FIXME 1):
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* Need a CoapResourceServer to maintain resources
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`CoapResourceServer resourceServer = new CoapResourceServer();`
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3. Instantiate a new TemperatureResource (Server.java, FIXME 2):
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* Resources are created like normal objects and added to the server
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`CoapResource resource = new CoapResource();`
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* Use the „Tasks“ view of Eclipse to find the right places
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* Solve only FIXME 1-3 as described by the following instructions - ignore other FIXMEs or TODOs
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4. Add the TemperatureResource to the ResourceServer (Server.java, FIXME 3):
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* Resources are created like normal objects and added to the server
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`resourceServer.createResource(resource);`
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5. Run the ResourceServer (Server.java):
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`resourceServer.start();`
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* Run Server: Click on Run -> Run in the Menu bar
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* To stop the server, press the red terminate button in the console/task area
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* Test it with Copper: coap://127.0.0.1
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* Stretch goal:
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** Create another resource type e.g.: humidity or current Time
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*** Tip: make a copy of „TemperatureResource.java“
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Client
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1. Establish a connection to the Server using the ChannelManager
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2. Create a CoapRequest & add some Options
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3. Send the CoapRequest
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4. Wait for CoapResponse
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5. Print the CoapResponse on the console (already done in our example)
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1. Establish a connection to the Server using the ChannelManager (Client.java, FIXME 4-5):
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* A client must implement CoapClient interface
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public class Client implements CoapClient {
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* A CoapChannelManager is used to manage different connections and to establish a connection to a server
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`channelManager = BasicCoapChannelManager.getInstance();`
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`clientChannel = channelManager.connect(CoapClient client,InetAddress serverIP, int serverPort);`
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2. Create a CoapRequest & add some Options (Client.java, FIXME 6-8):
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* A channel represents a single connection and is used to create and send requests
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`Boolean reliable = false;`
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`CoapRequestCode reqCode = CoapRequestCode.GET;`
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`CoapRequest request = clientChannel.createRequest(reliable,reqCode);`
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`request.setUriPath("/temperature");`
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3. Send the CoapRequest (Client.java, FIXME 6-8):
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`clientChannel.sendMessage(request);`
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4. Wait for CoapResponse & Print the CoapResponse on the console
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• A client has some callbacks that are invoked, when the corresponding event occurs
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`public void onConnectionFailed(...)`
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`public void onResponse(...) // = Unicast`
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`public void onMCResponse(...) // MC = Multicast`
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* Run Server: select Server.java and click on Run -> Run in the Menu bar
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* Run Client: select Client.java and click on Run -> Run in the Menu bar
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* Stretch goal:
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** GET the “/.well-known/core” resource (it is generated automatically by the server)
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** If you have written your own resources before: GET them
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## 5 Task 2: Implementation of a AC control by using the CoAP-observe mechanism
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1. Use the eventing mechanism CoAP-Observe
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2. Let the server notify clients every 5 seconds about a changed TemperatureResource
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3. Implement an Air Conditioner Resource with the path “/ACControl”, that can be set to “high”,
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“medium”, “low” or “off”
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28 <= Temperature -> high
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25 <= Temperature < 28 -> medium
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21 <= Temperature < 25 -> low
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Temperature < 21 -> off
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1. Use the eventing mechanism CoAP-Observe (Server.java, TODO 10):
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• Mark the TemperatureResource as observable
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`resource.setObservable(true);`
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2. Let server notify clients every 5 s about changed TemperatureResource (Server.java, TODO 11):
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* indicate a change for resource every 5 seconds
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`while (true) {
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try {Thread.sleep(5000);}
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catch (InterruptedException e) {/*do nothing*/}
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resource.changed();
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}`
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* Use the „Tasks“ view of Eclipse to find the right places
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* Solve only TODO 10-15 as described by the following instructions - ignore other TODOs or FIXMEs
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3. Implement an Air Conditioner Resource with the path “/ACControl”, that can be set to “high”,
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“medium”, “low” or “off” (Client.java & Server.java, TODO 12-15):
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* Change exitAfterResponse to false (Client.java, TODO 12)
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* Add the observe-option to your CoAP-GET request (Client.java, TODO 13)
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request.setObserveOption(0);
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* add a BasicCoapResource to the ResourceServer (Server.java, TODO 14)
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resourceServer.createResource( newBasicCoapResource(“/ACControl”,”off”,CoapMediaType.text_plain));
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* send PUT request (Client.java, TODO 15)
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`CoapRequest request = clientChannel.createRequest(true, CoapRequestCode.PUT);
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request.setUriPath(“/ACControl”);
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request.setContentType(CoapMediaType.text_plain);
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/*Depending on the received payload high, medium, low, off*/
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request.setPayload(“medium”.getBytes());
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clientChannel.sendMessage(request);`
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28 <= Temperature -> high
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25 <= Temperature < 28 -> medium
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21 <= Temperature < 25 -> low
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Temperature < 21 -> off |
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\ No newline at end of file |