问题
I want my Android app to behave as a client and listen on a particular port. None of the code I've tried works. I tried this tutorial to create a small chat app. The server side works fine, but the app crashes on my device. I have both my phone and server comp on VPN.
logcat text returned:
11-20 12:39:12.789: W/dalvikvm(12045): threadid=1: thread exiting with uncaught exception (group=0x4017c560)
11-20 12:39:12.799: E/AndroidRuntime(12045): FATAL EXCEPTION: main
11-20 12:39:12.799: E/AndroidRuntime(12045): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android_port/com.example.android_port.MainActivity}: java.lang.ClassNotFoundException: com.example.android_port.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.example.android_port-1.apk]
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1573)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.os.Looper.loop(Looper.java:130)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread.main(ActivityThread.java:3687)
11-20 12:39:12.799: E/AndroidRuntime(12045): at java.lang.reflect.Method.invokeNative(Native Method)
11-20 12:39:12.799: E/AndroidRuntime(12045): at java.lang.reflect.Method.invoke(Method.java:507)
11-20 12:39:12.799: E/AndroidRuntime(12045): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
11-20 12:39:12.799: E/AndroidRuntime(12045): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
11-20 12:39:12.799: E/AndroidRuntime(12045): at dalvik.system.NativeStart.main(Native Method)
11-20 12:39:12.799: E/AndroidRuntime(12045): Caused by: java.lang.ClassNotFoundException: com.example.android_port.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.example.android_port-1.apk]
11-20 12:39:12.799: E/AndroidRuntime(12045): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
11-20 12:39:12.799: E/AndroidRuntime(12045): at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
11-20 12:39:12.799: E/AndroidRuntime(12045): at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
11-20 12:39:12.799: E/AndroidRuntime(12045): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1565)
11-20 12:39:12.799: E/AndroidRuntime(12045): ... 11 more
来源：https://stackoverflow.com/questions/13468358/how-can-my-android-app-open-a-port-for-listening