Bluetooth with Xamarin Mac

I’ve been working on adding macOS support to 32feet.NET and there are two frameworks in macOS for Classic Bluetooth – IOBluetooth and IOBluetoothUI. I soon discovered that neither of these had bindings in the standard Xamarin.Mac package which is referenced by all Xamarin Mac applications. I decided to build binding libraries for both APIs and publish the code as part of 32feet.NET. This means you can either use the IOBluetooth lower-level APIs yourself or later use the platform-agnostic 32feet API.

Today I’ve published the first release of the InTheHand.IOBluetoothUI package. There are fewer APIs than IOBluetooth and I’ve already begun the manual process of simplifying and making it more “.NET friendly”. There is also documentation to add, though even Apple’s documentation on IOBluetooth is rather thin at best…

These are by no means final and there will be changes to the APIs as names are cleaned up and more is tested and fixed. If you’d like to try them in your projects please let me know your feedback via GitHub. Those NuGet packages are:-



Bluetooth from Unity

An ongoing issue with 32feet.NET is that it wouldn’t work inside Unity. The reason is that the System.Net.Sockets classes behave slightly differently in the Mono runtime to the desktop .NET framework and you can’t create a Socket using the Bluetooth specific address family.

In order to work around the issue it was necessary to P/Invoke into the native winsock functions, essentially rebuilding a subset of the Socket class. In parallel to this work I’ve been rebuilding 32feet with a more modern API which is less tied to Sockets (primarily just used on desktop Windows) and able to map onto a range of platforms. Another big change for this version is support for Bluetooth LE alongside classic Rfcomm on supported platform. Currently this library supports Xamarin Android and iOS along with UWP, Windows desktop .NET 4.6 and Mono .NET 2.0 for Unity. I’m working on a macOS implementation too. The API is essentially designed to be a more friendly version of the UWP API. In order to support such an old version of .NET, the Unity version is entirely synchronous whereas most of the API is normally async.

In order to test this I wrote a very simple script for Unity which picks a specific paired device, connects to a serial port service over Rfcomm and sends a string. Yes that’s right I have a 3d game that I can print from!

This is currently in preview (but available on NuGet now). There is a lot still to finish including generating the documentation. I’m hoping for some useful feedback, particularly on the Unity work but also any of the other current platforms. Feel free to join in the discussions on GitHub.

Windows Xamarin

Xamarin Forms Password Entry on Windows Runtime

Xamarin Forms doesn’t have a specific PasswordBox control – instead you use the Entry (Think TextBox) and set IsPassword to true. Normally this works as expected and provides a masked entry box. However there is a known issue on Windows Runtime (Phone and Desktop) where AutoSuggest and Auto Capitalisation are not disabled for a Password field. Luckily there is a workaround which is to set the input keyboard to Email. The small side effect is the addition of a “.com” button to the keyboard but it will stop the control capitalising the first letter or showing suggestions based on what you are typing. I added the following code behind:-

if(Device.OS == TargetPlatform.Windows)
   txtPassword.Keyboard = Keyboard.Email;

This issue doesn’t affect Silverlight apps (TargetPlatform.WinPhone) and I decided not to set the keyboard on other platforms as they work correctly with the default keyboard.


.NET 4.6 and DateTime extras

In case you missed it there is a great blog post on .NET 4.6 which is a part of Windows 10. Among the various performance and Hi-DPI improvements there are some more subtle enhancements. Perhaps as a nod to Microsoft’s new openness to other platforms there are some helper methods on DateTimeOffset for converting to and from UNIX times. These are represented as the number of seconds since 00:00 on the 1st of January 1970. I’d already come across situations where I needed this and had written a couple of simple conversion methods. They come in useful when doing interop with Android APIs for example. Why not match the .NET 4.6 API I thought so slightly tweaked them and put them in a Gist here:-

Windows Phone Xamarin

Windows Phone 8.1 Support in Xamarin Forms

Recently Xamarin Forms has been expanded to support Windows Phone 8.1 and Windows 8.1. There are instructions online for adding a Windows Phone 8.1 app to your solution and plugging it all together here:-

However there is a small omission which will lead to a build error – #6 tells you to remove the PhonePage base class from your MainPage definition but you actually need to replace it with:-

public sealed partial class MainPage : Xamarin.Forms.Platform.WinRT.WindowsPhonePage

WindowsPhonePage contains the LoadApplication method which you add in #7.

The instructions for Windows 8.1 require the same tweak except using WindowsPage instead of WindowsPhonePage


iRAPP Remote Desktop

Firstly, just to clarify, I don’t rap – this is a post about a useful Remote Desktop server for OSX. Wait, I hear you cry, you’re a Windows developer! Well that is true but I also use Xamarin to produce apps for iOS and Android and to build and deploy iOS apps you have to have a Mac in your workflow. Xamarin have done a great job to minimise this – you can do your development in Visual Studio on your PC but you have to connect to a Mac running their Build Server and you need to use the Mac to deploy apps to the iTunes store.

Because it was only for occasional interaction I don’t want the Mac Mini (which is a very nice looking piece of hardware BTW) setup with a Keyboard/Mouse/Monitor taking up space so it’s running as a headless device. I originally used TeamViewer to occasionally connect to the device but randomly last month the PC client started crashing on load and even an uninstall/reinstall wouldn’t get it working again so I looked for an alternative. I came across iRAPP by CodeRebel. I’d not heard of it before but it seemed perfect – it’s a Remote Desktop provider supporting Microsoft’s RDP protocol which means you can connect using the standard Windows Remote Desktop app. The app is available for Windows, Windows Phone, Android, Mac and iOS and since I use other Windows machines I have it installed on every device I use. By installing iRAPP on my Mac it just works in my Windows environment with no hassles. I found it very reliable over the trial period and have just purchased a license – $79 for a year and even that process is straight-forward and just works. Purchase the license online and click Update License from the iRAPP control panel and boom it’s up and running again!

There is also an iRAPP client for Windows which adds an extra dimension – it allows you to “blend” your desktop – switching to it adds the OSX menubar and dock to your desktop and will open apps in windows transparently on your desktop so you can feel like you are running OSX applications side by side with your Windows applications. Fun stuff but I didn’t really need this.

If you’re interested take a look here – There’s no ulterior motive here – I’m not receiving a commission or anything, I was just really impressed by the product and it’s proved reliable and useful.