23. December 2017

Courier: 556 Address unavailable

Courier Mail Server has many interesting features. One of the features is support for backscatter blacklist. It helps to protect the server from receiving emails which are not possible to deliver (e.g. in case of some problems with recipient’s account).

The common error message in that case is:

Courier: 556 Address unavailable

It’s not very straightforward how should an administrator resolve error 556. Even after fix of user’s account configuration, the message might appear and the Courier won’t accept an email even after restart. It could be even more confusing when Courier accepts email from some subnets, but it returns 556 Address unavailable on other subnets.

The resolution of the problem is simple: fix backscatter database.

Display list of addresses with on backscatter blacklist:

courier show all

Remove problematic address from the list:

courier clear user@domain

You can remove all addresses:

courier clear all

You can find more about backscatter blacklist in Courier’s documentation.

22. October 2017

SDL2_image for iOS with JPEG image format

Adding SDL2_image with JPEG support for iOS is a little bit different than for Android. In case of Android, it was necessary to add JPEG library in C and build it. iOS has JPEG dependency hidden in another library which is already compiled in frameworks.

If you just add SDL2_image to your project for iOS, you will very likely end up with following linker error:

"_kUTTypeJPEG", referenced from ...
Linker command failed with exit code 1

To resolve this issue, it is sufficient to add two dependencies into your project.

Go to Project and select Build Phases.

In the section Linking add library: ImageIO.framework

Then add the second dependency: MobileCoreServices.framework

Then Clean and Build the project.

These steps should resolve the linker issue, and JPEG should work.

7. September 2017

Gradle Experimental Plugin Android error: Cannot invoke method dependencies()

Update: Engineers at Google fixed the issue. Thank you.

After initial setup of SDL2 application for Android, I decided to add one activity before launching SDL. So I created the new MainActivity which should launch SDLActivity after a tap on the button.

This time Gradle Experimental Plugin gave me a very fancy error: Cannot invoke method dependencies() on null object.

As always the error message does not provide too many hints how to solve the issue.

Android Studio automatically just appended a dependency into the Gradle file during creation of new MainActivity. So the code in build.gradle looked like this:

tasks.whenTaskAdded { task ->
    if (task.name.contains('compile')) {
        task.dependsOn ':main:distributeLib'
    }
}dependencies {
    compile 'com.android.support.constraint:constraint-layout:+'
}

Little bit weird code for dependencies. The solution was just to add a new line.

tasks.whenTaskAdded { task ->
    if (task.name.contains('compile')) {
        task.dependsOn ':main:distributeLib'
    }
}

dependencies {
    compile 'com.android.support.constraint:constraint-layout:+'
}

The whole project is available at github.com/georgik/sdl2-android-example project.

More articles about SDL2 for Android are available under tag sdl2.

16. July 2017

Android Studio: Failure INSTALL_FAILED_TEST_ONLY

Starting application from Android Studio may fail with the mysterious message: Installation failed with message INSTALL_FAILED_TEST_ONLY.

The IDE will prompt you whether you want to uninstall the existing application.

Even this uninstallation may fail. When you open Run console, you can see something like this:

$ adb shell pm uninstall rocks.georgik.sdlapp
$ adb shell pm install -r "/data/local/tmp/rocks.georgik.sdlapp"
	pkg: /data/local/tmp/rocks.georgik.sdlapp
Failure [INSTALL_FAILED_TEST_ONLY]

$ adb shell pm uninstall rocks.georgik.sdlapp
DELETE_FAILED_INTERNAL_ERROR
Error while Installing APK

There is a relatively simple fix to this issue. Click drop-down menu with your configuration and choose Edit Configurations…

Select tab General and add -t to Install Flags field. Click Ok.

Now start the application again and it should work.

If this article didn’t help you to resolve your issue with Android Studio please let me know in comments below. There might be also other reasons for the error and we can discuss them.

9. December 2015

Thunderbird and Outlook solution of problem with Courier IMAP sslv3 alert illegal parameter

E-mail clients like Thunderbird or Outlook stopped to communicate with Courier IMAP/SMTP/POP TLS after some upgrade.

The only clue in log file was this error message:

courier couriertls: accept: error:14094417:SSL routines:ssl3_read_bytes:sslv3 alert illegal parameter

The problem was that certificate for IMAP (/etc/courier/imapd.pem) and /etc/courier/dhparam.pem were containing too short key. The short key was sufficient in past for encrypted communication. Unfortunately maintainers of Debian package forgot to add fix for upgrade.

It is very simple to fix the issue. Just generate DH with sufficient length.

DH_BITS=2048 mkdhparams

This command will update /etc/courier/dhparm.pem.

Make sure to update all pem files in case that they contain DH record.

Restart services and clients should be able to reconnect without problem.

If you still experience some issues with PEM files check out article PEM routines:PEM_read_bio:no start line.