Android with websocket communication (Node Websocket server and Android Java Client). Dosen't work on Android 4
android, android-4.0-ice-cream-sandwich, java, node.js, websocket
Solution
Don't connect to the Websocket on the main Thread (i.e. in `GameActivity.onCreate`) and the error will go away. You could use an `AsyncTask` to connect to the Websocket in the background.
Blocking the main thread by I/O operations (and network access is ultimately a I/O operation) will lead (in the worst case) to a sluggish user interface or Android killing your application because it didn't react timely. See the designing for responsiveness document.
Problem
I tried to use as a Android client Websocket - weberknecht with a thread to send every second a message to a Nodejs Websocket (js): Node WebSocket Server It work fine on android 2 or 2.3.3, but when i trie on android 4 i get an error on websocket.connect(); Do you know why or what i am doing wrong? My code is: ``` public class MainThread extends Thread { private boolean is_running; private URI url = null; private de.roderick.weberknecht.WebSocket websocket = null; public MainThread() { this.is_running = false; try { url = new URI("ws://192.168.1.88:8088/"); websocket = new WebSocketConnection(url); websocket.setEventHandler(new WebSocketEventHandler() { public void onOpen(){ System.out.println("--open"); } public void onMessage(WebSocketMessage message){ System.out.println("--received message: " + message.getText()); } public void onClose(){ System.out.println("--close"); } }); } catch (WebSocketException wse) { wse.printStackTrace(); //To change body of catch statement use File | Settings | File Templates. } catch (URISyntaxException use) { use.printStackTrace(); //To change body of catch statement use File | Settings | File Templates. } } @Override public void run() { while(is_running){ try { websocket.send("hello world"); Thread.sleep(10000); } catch (WebSocketException wse) { wse.printStackTrace(); } catch (InterruptedException e) { e.printStackTrace(); } } } public void set_running(boolean is_running) { if(is_running == true) try { websocket.connect(); this.is_running = is_running; } catch (WebSocketException e) { System.out.println(e.toString()); //e.printStackTrace(); } } } ``` and the error I get on android 4: ``` ERROR/AndroidRuntime(562): FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{com.biskis.test.websocket/com.biskis.test.websocket.GameActivity}: android.os.NetworkOnMainThreadException at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981) at android.app.ActivityThread.access$600(ActivityThread.java:123) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4424) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) at dalvik.system.NativeStart.main(Native Method) Caused by: android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099) at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84) at libcore.io.IoBridge.connectErrno(IoBridge.java:127) at libcore.io.IoBridge.connect(IoBridge.java:112) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) at java.net.Socket.startupSocket(Socket.java:566) at java.net.Socket.tryAllAddresses(Socket.java:127) at java.net.Socket.<init>(Socket.java:177) at java.net.Socket.<init>(Socket.java:149) at de.roderick.weberknecht.WebSocketConnection.createSocket(WebSocketConnection.java:238) at de.roderick.weberknecht.WebSocketConnection.connect(WebSocketConnection.java:83) at com.biskis.test.websocket.MainThread.set_running(MainThread.java:76) at com.biskis.test.websocket.GameActivity.onCreate(GameActivity.java:20) at android.app.Activity.performCreate(Activity.java:4465) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920) ... 11 more ``` Or do you know how to implement this in a better way to comunicate a client (java, android) to a server (nodejs, websocket) ? Thank you.