使用Coap实现android 局域网通信

Coap 简介

Coap是一种基于UDP的应用层协议。Coap支持RESTful规范，也就是支持URL方式访问，就像HTTP请求一样，支持GET,POST,PUT,DELETE，还支持订阅。详细可以看这里http://blog.csdn.net/xukai871105/article/details/17734163

Coap客户端

Coap客户端详细可以看这里的demo：https://github.com/eclipse/californium。
为了方便调试，我们使用火狐浏览器coap插件，地址：https://addons.mozilla.org/en-US/firefox/addon/copper-270430/。安装后如图:

服务端(android服务端)

使用开源的californium的SDK，github地址：https://github.com/eclipse/californium。
开启一个服务用来启动CoapServer：

public class ZHCoapService extends Service {
    private static final String TAG="ZHCoapService";
    private static final boolean DEBUG=true;
    private static final int HTTP_SERVER_PROXY_PORT = 8080;
    private static final int PORT =          NetworkConfig.getStandard().getInt(NetworkConfig.Keys.COAP_PORT);

    private static CoapServer mCoapServer;
    private ProxyHttpServer mHttpServer = null;
    private ForwardingResource coap2coap = new ProxyCoapClientResource("coap2coap");
    private ForwardingResource coap2http = new ProxyHttpClientResource("coap2http");
    private ZHDataObserve mDataObserve;
    private ZHQueryResource mQueryResource;

    private boolean isConnected=false;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();

        initCoapResource();

        IntentFilter intentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(connectReceiver, intentFilter);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Serializable serializable=intent.getSerializableExtra(Const.KEY_CMD);
        if(serializable != null && serializable instanceof ICmd){
            ICmd cmd=(ICmd) serializable;
            if(mDataObserve != null){
                //将消息通知客户端
                mDataObserve.change(cmd.getCmdString());
            }
        }
        return START_STICKY;
    }


    /**
     * 初始化CoapResource
     */
    private void initCoapResource() {
        mCoapServer = new CoapServer(PORT);
        mCoapServer.add(coap2coap);
        mCoapServer.add(coap2http);
        mQueryResource=new ZHQueryResource(getApplicationContext(),"query");
        mDataObserve=new ZHDataObserve("notify");
        mCoapServer.add(mDataObserve);
        mCoapServer.add(mQueryResource);
    }

    /**
     * 开启coap服务
     */
    private void startCoapServer() {
        try {
            stopCoapServer();
            if (mHttpServer == null)
                try {
                    mHttpServer = new ProxyHttpServer(HTTP_SERVER_PROXY_PORT);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            mHttpServer.setProxyCoapResolver(new DirectProxyCoapResolver(coap2coap));
            mCoapServer.start();
            if (DEBUG)
                Log.d(TAG, "CoapServer start");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 停止coap服务
     */
    private void stopCoapServer() {
        if (mCoapServer != null) {
            mCoapServer.stop();
            if (DEBUG)
                Log.d(TAG, "CoapServer stop");
        }
    }

    private BroadcastReceiver connectReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            State state = State.DISCONNECTED;
            if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
                ConnectivityManager contectivityMananger = (ConnectivityManager) context
                        .getSystemService(Context.CONNECTIVITY_SERVICE);
                NetworkInfo mNetworkInfo = contectivityMananger.getActiveNetworkInfo();
                if (mNetworkInfo != null && mNetworkInfo.isConnected()) {
                    state = mNetworkInfo.getState();
                }
            }
            if (state == State.CONNECTED &&!isConnected) {
                isConnected=true;
                startCoapServer();
            } else if (state == State.DISCONNECTED) {
                isConnected=false;
                stopCoapServer();
            }
        }
    };

    public void onDestroy() {
        unregisterReceiver(connectReceiver);
        super.onDestroy();
    };
}

在网络连接后启动coap服务。
在客户端上输入地址coap://ip:5683/，点击Discover即可查询出所有资源。
这里添加了2个资源“notify”和 “query”，其中“notify”有开通订阅功能，如图：

public class ZHDataObserve extends CoapResource {
    private String msg="";

    public ZHDataObserve(String name) {
        super(name);
        setObservable(true); // enable observing
        setObserveType(Type.NON); // configure the notification type to CONs
        getAttributes().setObservable(); // mark observable in the Link-Format
    }
    public  void change(String msg){
        this.msg=msg;
        if(getObserverCount()>0){
            changed();
        }
    }
    @Override
    public void handleGET(CoapExchange exchange) {
        exchange.respond(ResponseCode.CONTENT,msg,MediaTypeRegistry.TEXT_PLAIN);
    }
}

调用ZHDataObserve .change(“…”); 即可将消息通知到订阅者。

附上代码：
CoapDemo：CSDN
CoapDemo：github

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