[英]communication between Java server and Android client using Network Service Discovery
I'm building a Java server application (running on a pc) that register itself to the local network using JmDNS , and an Android client App that should discover the java server using Network Service Discovery . 我正在构建一个Java服务器应用程序(在PC上运行),它使用JmDNS将自己注册到本地网络,以及一个应该使用网络服务发现来发现java服务器的Android客户端应用程序。
When I run the android app first, and then run the java server, the app succeed to discover the registerd java server. 当我首先运行Android应用程序,然后运行java服务器时,应用程序成功发现注册的java服务器。
But when I first run the server and then the android app, the onDiscoveryStarted
method called but the onServiceFound
method never triggered - the android app doesn't discover the server. 但是当我第一次运行服务器然后运行Android应用程序时, onDiscoveryStarted
方法被调用但是onServiceFound
方法从未被触发 - android应用程序没有发现服务器。 This seems to me as an unexpected behavior. 这在我看来是一种意想不到的行为。
Succeed case : 成功案例 :
Android app log: Android应用日志:
08-24 22:42:06.157 NSD_DISCOVER onCreate 08-24 22:42:06.157 NSD_DISCOVER onCreate
08-24 22:42:06.373 NSD_DISCOVER﹕ onDiscoveryStarted Service discovery started 08-24 22:42:06.373 NSD_DISCOVER:onDiscoveryStarted服务发现已启动
08-24 22:42:30.256 NSD_DISCOVER﹕ onServiceFound Known Service Type: _http._tcp. 08-24 22:42:30.256 NSD_DISCOVER:onServiceFound已知服务类型:_http._tcp。
08-24 22:42:30.293 NSD_DISCOVER﹕ onServiceResolved Resolve Succeeded. 08-24 22:42:30.293 NSD_DISCOVER:onServiceResolved Resolve Succeeded。 name: NsdApp, type: ._http._tcp, host: /10.0.0.2, port: 52288 name:NsdApp,type:._ http._tcp,host:/10.0.0.2,port:52288
Java server log: Java服务器日志:
START 开始
REGISTERED 注册
END 结束
WAITING_FOR_MESSAGE WAITING_FOR_MESSAGE
hello world 你好,世界
END_THREAD END_THREAD
Failure case : 失败案例 :
Android app log: Android应用日志:
08-24 22:05:21.690 NSD_DISCOVER﹕ onCreate 08-24 22:05:21.690 NSD_DISCOVER:onCreate
08-24 22:05:21.908 NSD_DISCOVER﹕ onDiscoveryStarted Service discovery started 08-24 22:05:21.908 NSD_DISCOVER:onDiscoveryStarted服务发现开始了
Java server log: Java服务器日志:
START 开始
REGISTERED 注册
END 结束
WAITING_FOR_MESSAGE WAITING_FOR_MESSAGE
Server code 服务器代码
public class Server {
public static String mServiceName = "NsdApp";
public static final String SERVICE_TYPE = "_http._tcp.local";
static ServerSocket mServerSocket;
public static void main(String[] args) throws IOException {
System.out.println("START");
try {
mServerSocket = new ServerSocket(0);
} catch (IOException e) {
System.out.println("ServerSocket(0) FAILED");
}
int mPort = mServerSocket.getLocalPort();
JmDNS jmdns = JmDNS.create();
ServiceInfo info = ServiceInfo.create(SERVICE_TYPE, mServiceName, mPort, "B");
jmdns.registerService(info);
System.out.println("REGISTERED");
jmdns.close();
Thread mReceiveMessage = new Thread(new ReceiveMessage());
mReceiveMessage.start();
System.out.println("END");
}
public static class ReceiveMessage implements Runnable {
public void run() {
System.out.println("WAITING_FOR_MESSAGE");
try {
Socket clientSocket = mServerSocket.accept();
InputStreamReader inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String message = bufferedReader.readLine();
System.out.println(message);
bufferedReader.close();
inputStreamReader.close();
clientSocket.close();
System.out.println("END_THREAD");
} catch (IOException ex) {
System.out.println("Problem in message reading");
}
}
}
}
Client code 客户代码
public class MainActivity extends Activity {
public static final String TAG = "NSD_DISCOVER";
public static final String SERVICE_TYPE = "_http._tcp.";
NsdManager.DiscoveryListener mDiscoveryListener;
NsdManager.ResolveListener mResolveListener;
NsdManager mNsdManager;
int port;
InetAddress host;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.v(TAG, "onCreate");
mNsdManager = (NsdManager) getSystemService(Context.NSD_SERVICE);
initializeResolveListener();
initializeDiscoveryListener();
mNsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener);
}
public void initializeDiscoveryListener() {
mDiscoveryListener = new NsdManager.DiscoveryListener() {
@Override
public void onDiscoveryStarted(String regType) {
Log.v(TAG, "onDiscoveryStarted Service discovery started");
}
@Override
public void onServiceFound(NsdServiceInfo service) {
if (!service.getServiceType().equals(SERVICE_TYPE)) {
Log.v(TAG, "onServiceFound Unknown Service Type: " + service.getServiceType());
} else {
Log.v(TAG, "onServiceFound Known Service Type: " + service.getServiceType());
mNsdManager.resolveService(service, mResolveListener);
}
}
@Override
public void onServiceLost(NsdServiceInfo service) {
Log.e(TAG, "service lost" + service);
}
@Override
public void onDiscoveryStopped(String serviceType) {
Log.i(TAG, "Discovery stopped: " + serviceType);
}
@Override
public void onStartDiscoveryFailed(String serviceType, int errorCode) {
Log.e(TAG, "Discovery failed: Error code:" + errorCode);
mNsdManager.stopServiceDiscovery(this);
}
@Override
public void onStopDiscoveryFailed(String serviceType, int errorCode) {
Log.e(TAG, "Discovery failed: Error code:" + errorCode);
mNsdManager.stopServiceDiscovery(this);
}
};
}
public void initializeResolveListener() {
mResolveListener = new NsdManager.ResolveListener() {
@Override
public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
Log.e(TAG, "onResolveFailed Resolve failed" + errorCode);
}
@Override
public void onServiceResolved(NsdServiceInfo serviceInfo) {
Log.v(TAG, "onServiceResolved Resolve Succeeded. " + serviceInfo);
port = serviceInfo.getPort();
host = serviceInfo.getHost();
SendMessage sendMessageTask = new SendMessage();
sendMessageTask.execute();
}
};
}
private class SendMessage extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
try {
Socket client;
PrintWriter printwriter;
client = new Socket(host, port);
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write("hello world");
printwriter.flush();
printwriter.close();
client.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
} }
You are calling jmdns.close()
right after registering. 您在注册后立即调用jmdns.close()
。 Your service is only discoverable as long as you have jmdns open. 只要您打开jmdns,您的服务才能被发现。 You should remove that call to close
, make your jmdns
variable a member of your class, and then only call close on it when you don't want your services to be discoverable anymore. 您应该删除该调用以close
,使您的jmdns
变量成为您的类的成员,然后只在您不希望您的服务被发现时才调用close。 Also, it is good form to call unregisterAllServices()
before closing jmdns. 此外,在关闭jmdns之前调用unregisterAllServices()
是一种很好的形式。
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