常用的连接方式

1. 通过NSD_SERVICE连接，Socket通信，这种方式的前提是设备都必须连接在同一个wifi下。

1. 通过NSD_SERVICE连接

   其中一台设备作为服务端，需要向NSD_SERVICE注册服务，另一台设备作为客户端，通过NSD_SERVICE搜索服务，连接服务，连接之后就可以通过Socket通信了。

   向NSD_SERVICE注册服务：

   NsdServiceInfo serviceInfo = new NsdServiceInfo();
    serviceInfo.setServiceName("NsdChat");
    serviceInfo.setServiceType("_http._tcp.");
    serviceInfo.setPort(SERVER_PORT);
   
    nsdManager.registerService(
            serviceInfo, NsdManager.PROTOCOL_DNS_SD, new NsdManager.RegistrationListener() {
                @Override
                public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
                    Log.e(TAG, "nsdRegist onRegistrationFailed: " + errorCode);
                }
   
                @Override
                public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
                    Log.e(TAG, "nsdRegist onUnregistrationFailed: " + errorCode);
                }
   
                @Override
                public void onServiceRegistered(NsdServiceInfo serviceInfo) {
                    Log.d(TAG, "nsdRegist onServiceRegistered");
                }
   
                @Override
                public void onServiceUnregistered(NsdServiceInfo serviceInfo) {
                    Log.d(TAG, "nsdRegist onServiceUnregistered");
                }
            });
   
    serviceType 用于客户端搜索时的检索条件
    SERVER_PORT为端口号，客户端能获取到，服务端Socket也是监听这个端口（这段代码就不贴了）
   

   客户端代码

   1. 搜索设备

       nsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, new NsdManager.DiscoveryListener() {
       @Override
       public void onStartDiscoveryFailed(String serviceType, int errorCode) {
           Log.e(TAG, "discoverNsdService onStartDiscoveryFailed " + errorCode);
       }
      
       @Override
       public void onStopDiscoveryFailed(String serviceType, int errorCode) {
           Log.e(TAG, "discoverNsdService onStopDiscoveryFailed " + errorCode);
       }
      
       @Override
       public void onDiscoveryStarted(String serviceType) {
           Log.d(TAG, "discoverNsdService onDiscoveryStarted");
       }
      
       @Override
       public void onDiscoveryStopped(String serviceType) {
           Log.d(TAG, "discoverNsdService onDiscoveryStopped");
       }
      
       @Override
       public void onServiceFound(NsdServiceInfo serviceInfo) {
           Log.d(TAG, "discoverNsdService onServiceFound");
           resolveService(serviceInfo);
       }
      
       @Override
       public void onServiceLost(NsdServiceInfo serviceInfo) {
           Log.d(TAG, "discoverNsdService onServiceLost");
       }
       });
      

   2. 连接设备

    nsdManager.resolveService(serviceInfo, new NsdManager.ResolveListener() {
        @Override
        public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
            Log.e(TAG, "resolveService onResolveFailed " + errorCode);
        }
   
        @Override
        public void onServiceResolved(NsdServiceInfo serviceInfo) {
            Log.d(TAG, "resolveService onServiceResolved");
            sendSocketNsd(serviceInfo);
        }
    });
   

   3. 发送Socket信息

    try {
        Socket socket = new Socket(serviceInfo.getHost(), serviceInfo.getPort());
        DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
        DataInputStream inputStream = new DataInputStream(socket.getInputStream());
        outputStream.writeUTF("from haha usb oo ");
   
        String str = inputStream.readUTF();
        Log.d(TAG, "socket receive: " + str);
   
        socket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }