Today's project from Joost van Schaik is a Hardware Friday, a Mobile Monday and Windows Wednesday project all wrapped up in one post. WiFi Direct, NFC, Bluetooth, Windows 8, 8.1 and Windows Phone 8 and some code to help you build apps that talk between them all.

On my way to the November 2013 MVP Summit, at Matthijs Hoekstra’s house in Sammamish, and back again in the Netherlands I spent considerable time trying to get my tap+send and Bluetooth connection helper to not only work on Windows 8.1 as well, but also to make it provide cross-platform communication between Windows Phone 8 and Windows 8.1. Unfortunately the MSDN PixPresenter sample suggest you can connect between Windows Phone and Windows 8 by sharing app ids in the PeerFinder.AlternateIdentities property, and so does the MSDN documentation on said property. That way, my friends, lay only mud pies and frustration. I don’t doubt that it will work for tap+send, but as the majority of the current Windows 8.x devices (including Microsoft’s own excellent Surface devices) do not include NFC capabilities, the chances of making a successful connection between a Windows Phone and a random Windows 8 computer using tap+send are very small.

I seem to have a thing with Italians these days – I had a lot of fun with a bunch of them at the Summit, and it was not until this Italian developer called Andrea Boschin pointed me to a recent blog post by him that I found a way out of this. Using this knowledge I adapted DevicePairConnectionHelper once again, so now it’s not only cross platform, but it can also connect between Windows Phone 8 and Windows 8.1. If you are completely new to this subject, I suggest you read the previous two articles about this subject as well.

What it can do

In the demo solution, that sports both a Windows 8.1 Store application and a Windows Phone 8 application, you will find a shared file DevicePairConnectionHelper2.cs containing the updated DevicePairConnectionHelper – now supporting the following communication paths:

Windows Phone 8 to Windows Phone 8 – tap+send

Windows Phone 8 to Windows Phone 8 – Bluetooth browsing

Windows 8.1 to Windows 8.1 – WifiDirect browsing

Windows 8.1 to Windows Phone 8 – Bluetooth.

In theory it should support Windows 8.1 to Windows 8.1 over tap+send as well, but lacking even a single NFC enabled Windows 8.1 device, this is hard to test for me.

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How to set it up and use it

A very important precondition– the devices can only find each other when the phone is paired to the Windows 8.1 computer. Now the odd thing is – as you have paired the phone to the computer, you will see that is “connected” on both the computer and the phone, for a very short time. And then it flashes off again, so they are not connected. This is a bit confusing, but it is normal. They now ‘know’ each other, and that is what’s important.

As far as the the updated DevicePairConnectionHelper goes, it works nearly the same as the previous one, but it has two extras, as far as using it is concerned.

In the constructor, you can now optionally provide a GUID that describes a Bluetooth Service

There is a new boolean property ConnectCrossPlatform that you can set to true – then the Window 8 phone will try to connect to a Windows 8 machine using Bluetooth.

To set it up, you have to take the following things into account:

In you Windows Phone 8 app manifest, you have to select the ID_CAP_PROXIMITY capability

In you Windows 8 app manifest, you will have to the following capabilities Private Networks (Client & Server) Proximity

After you have saved you manifest, you have to open the Package.appmanifest manually (right click, hit View Code) and add a Bluetooth rfcomm service. Andrea explains how this is done, and I repeat it here for completeness:

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And that’s about what I needed to do. The changes to the sample app are very limited – I added a checkbox on both of them, and a wrapping ConnectCrossPlatform property that is set by said checkbox. Also a minor detail – the Reset method in the NfcConnectViewModel no longer stops the PeerFinder first. This is especially important for the Windows 8.1 app – it never finds the phone, but the phone is still trying to make a connection. If the PeerFinder on Windows 8.1 is already stopped, you get all kind of funky errors when you select the computer on the phone.

For those who find the discussion a bit arcane – there is, as always, a working demo solution for this article. It is built on top of my new not-yet-published WpWinNl library – that’s basically a cross-platform (no, not PCL, just a NuGet Package) version of the wp7nl library. Well as cross platform as it can be. Stay tuned, it will be available soon. But tackling this problem took a bit longer than I hoped, so I am a bit behind schedule