android nsd服务

全称为: Network Service Discovery.

作用为: The addition of Network Service Discovery (NSD) takes this further by allowing an application to seek out a nearby device running services with which it can communicate. (也就是说使用这个服务就可以搜索附近哪个设备可以进行通信).

关于NSD的开发笔记.

1. 注册自己的服务, 目的是设定协议以及端口. 只有设定好了自己的服务属性, 才能进行下一步的网络服务匹配.
2. 发现网络内的各个服务.
   需要注意的是在发现监听器(DiscoveryListener)里, 当某个service找到的时候, 需要做一些条件判断:类型匹配, 服务名字匹配这样的操作. 当服务名字完全一致的时候, 说明自己被找到了, 要过滤掉. 也就是说, 查找目标也包括自己.
3. 发现流程:
   (1) 注册nsd服务.
   (2) 初始化注册监听器
   (3) 初始化发现监听器
   (4) 初始化处理监听器
   (5) 注销nsd服务
4. 具体实现代码如下(借鉴自官方教程):
   (1)

    public void registerService(int port) {
        NsdServiceInfo serviceInfo = new NsdServiceInfo();
        serviceInfo.setServiceName(NSD_SERVICE_NAME);
        serviceInfo.setPort(port);
        serviceInfo.setServiceType(NSD_SERVER_TYPE);

        mNsdManager = (NsdManager) mCurrentContext.getSystemService(Context.NSD_SERVICE);
        mNsdManager.registerService(serviceInfo, NsdManager.PROTOCOL_DNS_SD, mRegistrationListener);
    }

(2)

    public void initializeRegistrationListener() {
        mRegistrationListener = new NsdManager.RegistrationListener() {
            @Override
            public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {

            }

            @Override
            public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {

            }

            @Override
            public void onServiceRegistered(NsdServiceInfo serviceInfo) {
                mServerName = serviceInfo.getServiceName();
            }

            @Override
            public void onServiceUnregistered(NsdServiceInfo serviceInfo) {

            }
        };
    }

(3)

    public void initializeDiscoveryListener() {
        mDiscoveryListener = new NsdManager.DiscoveryListener() {
            @Override
            public void onStartDiscoveryFailed(String serviceType, int errorCode) {
                mNsdManager.stopServiceDiscovery(this);
            }

            @Override
            public void onStopDiscoveryFailed(String serviceType, int errorCode) {
                mNsdManager.stopServiceDiscovery(this);
            }

            @Override
            public void onDiscoveryStarted(String serviceType) {

            }

            @Override
            public void onDiscoveryStopped(String serviceType) {

            }

            @Override
            public void onServiceFound(NsdServiceInfo serviceInfo) {
                if (!serviceInfo.getServiceType().equals(NSD_SERVER_TYPE)) {

                } else if (serviceInfo.getServiceName().equals(NSD_SERVICE_NAME)) {

                } else if (serviceInfo.getServiceName().contains(NSD_SERVICE_NAME)) {
                    mNsdManager.resolveService(serviceInfo, mResolverListener);
                }
            }

            @Override
            public void onServiceLost(NsdServiceInfo serviceInfo) {

            }
        };
    }

(4)

    public void initializeResolveListener() {
        mResolverListener = new NsdManager.ResolveListener() {
            @Override
            public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {

            }

            @Override
            public void onServiceResolved(NsdServiceInfo serviceInfo) {
                if (serviceInfo.getServiceName().equals(mServerName)) {
                    Log.d(logTitle, "Same IP.");
                    return;
                }
                mService = serviceInfo;
                int port = mService.getPort();
                InetAddress host = mService.getHost();
            }
        };
    }

(5)

    public void unInitService() {
        mNsdManager.unregisterService(mRegistrationListener);
        mNsdManager.stopServiceDiscovery(mDiscoveryListener);
    }