sockets - Android Development - Why is this application crashing? -


i've made small android application sends udp packet moment open it.

the problem is, crashes when open it, instead of sending packet.

i mean, i've tried running on eclipse's android virtual device, , crashes there.

here's code:

package com.example.messagesender;  import android.os.bundle; import android.view.menu; import android.view.view; import android.widget.button; import android.widget.edittext; import android.widget.textview; import android.app.activity;  import java.io.*; import java.net.*;  public class message_sender extends activity {     datagramsocket clientsocket;     inetaddress ipaddressx;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_message__sender);         try {             clientsocket = new datagramsocket();         } catch (socketexception e) {             // todo auto-generated catch block             e.printstacktrace();         }           try {             ipaddressx = inetaddress.getbyname("127.0.0.1");         } catch (unknownhostexception e) {             e.printstacktrace();         }           byte[] senddata = new byte[1024];           string sentence = "hello world!";           senddata = sentence.getbytes();           datagrampacket sendpacket = new datagrampacket(senddata, senddata.length, ipaddressx, 12345);           try {             clientsocket.send(sendpacket);         } catch (ioexception e) {             // todo auto-generated catch block             e.printstacktrace();         }     }      @override     public boolean oncreateoptionsmenu(menu menu) {         // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.menu.message__sender, menu);         return true;     }  }

logcat output:

01-31 19:00:58.420: w/system.err(810): java.net.socketexception: socket failed: eacces (permission denied) 01-31 19:00:58.420: w/system.err(810):  @ libcore.io.iobridge.socket(iobridge.java:576) 01-31 19:00:58.420: w/system.err(810):  @ java.net.plaindatagramsocketimpl.create(plaindatagramsocketimpl.java:91) 01-31 19:00:58.420: w/system.err(810):  @ java.net.datagramsocket.createsocket(datagramsocket.java:133) 01-31 19:00:58.540: w/system.err(810):  @ java.net.datagramsocket.<init>(datagramsocket.java:80) 01-31 19:00:58.540: w/system.err(810):  @ java.net.datagramsocket.<init>(datagramsocket.java:65) 01-31 19:00:58.540: w/system.err(810):  @ com.example.messagesender.message_sender.oncreate(message_sender.java:23) 01-31 19:00:58.540: w/system.err(810):  @ android.app.activity.performcreate(activity.java:5231) 01-31 19:00:58.540: w/system.err(810):  @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1087) 01-31 19:00:58.540: w/system.err(810):  @ android.app.activitythread.performlaunchactivity(activitythread.java:2159) 01-31 19:00:58.540: w/system.err(810):  @ android.app.activitythread.handlelaunchactivity(activitythread.java:2245) 01-31 19:00:58.540: w/system.err(810):  @ android.app.activitythread.access$800(activitythread.java:135) 01-31 19:00:58.540: w/system.err(810):  @ android.app.activitythread$h.handlemessage(activitythread.java:1196) 01-31 19:00:58.540: w/system.err(810):  @ android.os.handler.dispatchmessage(handler.java:102) 01-31 19:00:58.540: w/system.err(810):  @ android.os.looper.loop(looper.java:136) 01-31 19:00:58.590: w/system.err(810):  @ android.app.activitythread.main(activitythread.java:5017) 01-31 19:00:58.590: w/system.err(810):  @ java.lang.reflect.method.invokenative(native method) 01-31 19:00:58.590: w/system.err(810):  @ java.lang.reflect.method.invoke(method.java:515) 01-31 19:00:58.590: w/system.err(810):  @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:779) 01-31 19:00:58.590: w/system.err(810):  @ com.android.internal.os.zygoteinit.main(zygoteinit.java:595) 01-31 19:00:58.590: w/system.err(810):  @ dalvik.system.nativestart.main(native method) 01-31 19:00:58.590: w/system.err(810): caused by: libcore.io.errnoexception: socket failed: eacces (permission denied) 01-31 19:00:58.610: w/system.err(810):  @ libcore.io.posix.socket(native method) 01-31 19:00:58.610: w/system.err(810):  @ libcore.io.blockguardos.socket(blockguardos.java:181) 01-31 19:00:58.610: w/system.err(810):  @ libcore.io.iobridge.socket(iobridge.java:561) 01-31 19:00:58.610: w/system.err(810):  ... 19 more 01-31 19:00:58.630: d/androidruntime(810): shutting down vm 01-31 19:00:58.630: w/dalvikvm(810): threadid=1: thread exiting uncaught exception (group=0xb1a86ba8) 01-31 19:00:58.640: e/androidruntime(810): fatal exception: main 01-31 19:00:58.640: e/androidruntime(810): process: com.example.messagesender, pid: 810 01-31 19:00:58.640: e/androidruntime(810): java.lang.runtimeexception: unable start activity componentinfo{com.example.messagesender/com.example.messagesender.message_sender}: java.lang.nullpointerexception 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread.performlaunchactivity(activitythread.java:2195) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread.handlelaunchactivity(activitythread.java:2245) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread.access$800(activitythread.java:135) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread$h.handlemessage(activitythread.java:1196) 01-31 19:00:58.640: e/androidruntime(810):  @ android.os.handler.dispatchmessage(handler.java:102) 01-31 19:00:58.640: e/androidruntime(810):  @ android.os.looper.loop(looper.java:136) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread.main(activitythread.java:5017) 01-31 19:00:58.640: e/androidruntime(810):  @ java.lang.reflect.method.invokenative(native method) 01-31 19:00:58.640: e/androidruntime(810):  @ java.lang.reflect.method.invoke(method.java:515) 01-31 19:00:58.640: e/androidruntime(810):  @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:779) 01-31 19:00:58.640: e/androidruntime(810):  @ com.android.internal.os.zygoteinit.main(zygoteinit.java:595) 01-31 19:00:58.640: e/androidruntime(810):  @ dalvik.system.nativestart.main(native method) 01-31 19:00:58.640: e/androidruntime(810): caused by: java.lang.nullpointerexception 01-31 19:00:58.640: e/androidruntime(810):  @ com.example.messagesender.message_sender.oncreate(message_sender.java:38) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activity.performcreate(activity.java:5231) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1087) 01-31 19:00:58.640: e/androidruntime(810):  @ android.app.activitythread.performlaunchactivity(activitythread.java:2159) 01-31 19:00:58.640: e/androidruntime(810):  ... 11 more

so why crashing? code looks fine me, it's weird.

it looks trying make network calls on ui thread, big no no.

take @ how implement network operations using background threads, asynctask there literaly 1000's of questions , examples this.

here tutorial started

also add necessary permission manifest

<uses-permission android:name="android.permission.internet" />

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