Java – (a) Smack returned “service-unavailable (503)” error at login ()

I’m trying to implement a simple jabber messenger on Android using the asmack library. Here is the code:

public boolean login()
{
    if (connection != null && connection.isConnected())
    {
        Log.i("XMPP", connection.getHost());
        try 
        {
            connection.login(USERNAME, PASSWORD);
        } 
        catch (XMPPException e) 
        {
            e.printStackTrace();
            return false;
        }
        return true;
    }
    return false;
}

The exception I got after connection.login() (the connection looks fine):

service-unavailable(503)
at org.jivesoftware.smack.NonSASLAuthentication.authenticate(NonSASLAuthentication.java:77)
at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:239)
at org.jivesoftware.smack.Connection.login(Connection.java:353)
at com.someapp.networking.XMPPMessenger.login(XMPPMessenger.java:60)
at com.someapp.XMPPService.onCreate(XMPPService.java:33)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2780)
at android.app.ActivityThread.access$3200(ActivityThread.java:119)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1917)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4363)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
at dalvik.system.NativeStart.main(Native Method)

What could be the error?

Asmack is able to establish a new connection to the server, but it belongs to Non-SASL mode for some reason (call NonSASLAuthentication.authenticate(NonSASLAuthentication.java:77) ).
I think that’s what the server is trying to tell you with a “service-unavailable(503)” response, i.e. it doesn’t support non-SASL authentication.

Try debugging why smack does not attempt SASL authentication.

Note: The lines in the smack source code viewer are a bit off track because of the deviation from different versions and patches from asmack.