Javalin: Running server on Android using Javalin

[vikascn]

@tipsy @felislynx-silae @robinvanyang

I am trying to run a web server on an Android device using the Javalin framework.

What do i need to make it work ? I followed the suggestions from https://github.com/tipsy/javalin/issues/185. (Since that issue was closed, i am raising a new one.)
I am getting below error while starting the server ->

W/System.err: [main] INFO io.javalin.Javalin - Starting Javalin ... com.example.javalin W/System.err: [main] ERROR io.javalin.Javalin - Failed to start Javalin com.example.javalin D/AndroidRuntime: Shutting down VM com.example.javalin E/AndroidRuntime: FATAL EXCEPTION: main
`

Process: com.example.javalin, PID: 18133
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.javalin/com.example.javalin.MainActivity}: java.lang.RuntimeException: Port 1-1023 require elevated privileges (process must be started by admin).
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2951)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3086)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6718)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
 Caused by: java.lang.RuntimeException: Port 1-1023 require elevated privileges (process must be started by admin).
    at io.javalin.Javalin.start(Javalin.java:159)
    at io.javalin.Javalin.start(Javalin.java:119)
    at com.example.javalin.HelloWorld.main(HelloWorld.java:9)
    at com.example.javalin.MainActivity.onCreate(MainActivity.java:17)
    at android.app.Activity.performCreate(Activity.java:7144)
    at android.app.Activity.performCreate(Activity.java:7135)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2931)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3086) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6718) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
 Caused by: java.net.SocketException: Permission denied
    at sun.nio.ch.Net.socket0(Native Method)
    at sun.nio.ch.Net.serverSocket(Net.java:424)
    at sun.nio.ch.ServerSocketChannelImpl.<init>(ServerSocketChannelImpl.java:88)
    at sun.nio.ch.SelectorProviderImpl.openServerSocketChannel(SelectorProviderImpl.java:56)
    at java.nio.channels.ServerSocketChannel.open(ServerSocketChannel.java:108)
    at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:336)
    at org.eclipse.jetty.server.ServerConnector.open(ServerConnector.java:308)
    at org.eclipse.jetty.server.AbstractNetworkConnector.doStart(AbstractNetworkConnector.java:80)
    at org.eclipse.jetty.server.ServerConnector.doStart(ServerConnector.java:236)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.server.Server.doStart(Server.java:394)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at io.javalin.core.util.JettyServerUtil.initialize(JettyServerUtil.kt:110)
    at io.javalin.Javalin.start(Javalin.java:140)
    at io.javalin.Javalin.start(Javalin.java:119) 
    at com.example.javalin.HelloWorld.main(HelloWorld.java:9) 
    at com.example.javalin.MainActivity.onCreate(MainActivity.java:17) 
    at android.app.Activity.performCreate(Activity.java:7144) 
    at android.app.Activity.performCreate(Activity.java:7135) 
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2931) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3086) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6718) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

`

Here is my code :

Build.gradle:

`
compileSdkVersion 28

defaultConfig {
    applicationId "com.example.javalin"
    minSdkVersion 28
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}

`

compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 }

implementation 'io.javalin:javalin:2.8.0' implementation 'org.slf4j:slf4j-simple:1.7.26'

gradle.properties

android.enableD8=true

HelloWorld.java . <- has the server

`import io.javalin.Javalin;

public class HelloWorld {
public static void main() {

    Javalin app = Javalin.create();
    app.start(8080);
    app.get("/", ctx -> ctx.result("Hello World"));
}

}`

MainActivity.java <- calls HelloWorld to start the server

`public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    HelloWorld.main();

}
}

[tipsy]

Your error message doesn't match your code, it says Caused by: java.lang.RuntimeException: Port 1-1023 require elevated privileges (process must be started by admin).. but your code shows port 8080. Are you sure you're trying to start the server on 8080?

[vikascn]

Was missing the internet permission.

Worked after adding in Manifest file
<uses-permission android:name="android.permission.INTERNET"/>

Any idea why it would work only on Android API level 28 ?

[tipsy]

I think Jetty uses some Java APIs that aren't available for older versions of Android.

[vikascn]

thanks @tipsy for the quick response.