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我愿意使用 CoAP 协议来实现基于 Java 推送的消息传递系统。特别是在这样的系统中，客户端只打开一次与服务器（资源）的连接，并且服务器以特定速率（例如，每秒 10 条消息）推送消息（“不可确认”）。但是我没有找到任何现有的解决方案来构建上述系统。

我发现的是基于拉的消息传递系统。对于这种情况，客户端打开与服务器的连接，一段时间后客户端发送 GET 请求。然后，服务器处理请求并将单个消息推送（作为响应）给客户端。

因此，对于每个 GET，我都有一条消息作为响应——即双向异步交互。

有人知道如何使用 CoAP 实现基于推送的消息系统吗？CoAP 是否支持这样的系统？

基于拉取的消息系统实现如下

  1. 服务器部分

        public class CoapServerPartAsync extends CoapServer {

              private static final int COAP_PORT = 8891;
              private static int incrementor = 1;
              /*
              * Application entry point.
              */
              public static void main(String[] args) {

                 try {

                 // create server
                 CoapServerPartAsync server = new CoapServerPartAsync();

                 // add endpoints on all IP addresses

                 server.addEndpoints();

                 server.start();

                 } catch (SocketException e) {

                      System.err.println("Failed to initialize server: " +   e.getMessage());
                 }
              }

             /**
              * Add endpoints listening on default CoAP port on all IP  addresses of all network interfaces.
              *  
              * @throws SocketException if network interfaces cannot be determined
              */

              private void addEndpoints() throws SocketException {


                  InetSocketAddress bindToAddress = new  InetSocketAddress("127.0.0.1", COAP_PORT);

                 addEndpoint(new CoapEndpoint(bindToAddress));

                 }

                /*
                 * Constructor for a new Hello-World server. Here, the resources
                 * of the server are initialized.
                 */
                 public CoapServerPartAsync() throws SocketException {

                 // provide an instance of a Hello-World resource
                 add(new HelloWorldResource());
                 }

               /*
                * Definition of the Hello-World Resource
               */

                class HelloWorldResource extends CoapResource {

                      public HelloWorldResource() {

                      // set resource identifier
                      super("helloWorld");

                     // set display name
                     getAttributes().setTitle("Hello-World Resource");
                 }

                 @Override
                 public void handleGET(CoapExchange exchange){

                 // respond to the request
                 System.out.println("Push [Hello World!"+(incrementor)+"]");
                  exchange.respond("Hello World!"+(incrementor));
                  incrementor++;

            }
       }
 }

  2. 客户端部分

          public class CoapClientPartAsync {

                    // static boolean getResponse = false;

                    public static void main(String args[]) { 

                    CoapClient client = new CoapClient("coap://127.0.0.1:8891/helloWorld").useNONs();

                   while(true){
                      CoapObserveRelation relation = client.observe( 
         new CoapHandler() {

                 @Override public void onLoad(CoapResponse response){
                            String content = response.getResponseText();
                           System.out.println("NOTIFICATION: " + content);

                          }

                    @Override public void onError() {
                    System.err.println("OBSERVING FAILED (press enter to exit)");
                  }
               });
               try {
                     Thread.sleep(1000);
                 }catch (InterruptedException e) {
                      // TODO Auto-generated catch block
                      e.printStackTrace();
                 }       
           }
       }
  }
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0 回答 0