C# 4 and .NET 4

1352 ❘ ChaPTer 45 peer-tO-peer netwOrkinG
}
PeerList.Items.Clear();
RefreshButton.IsEnabled = false;
// Resolve unsecured peers asynchronously
resolver.ResolveAsync(new PeerName("0.P2P Sample"), 1);
The remainder of the code is responsible for displaying and communicating with peers, and you can explore
it at your leisure.
Exposing WCF endpoints through P2P clouds is a great way of locating services within an enterprise, as
well as being an excellent way to communicate between peers, as in this example.
system.net.PeerToPeer.Collaboration
The classes in the System.Net.PeerToPeer.Collaboration namespace provide a framework you can use
to create applications that use the People Near Me service and the P2P collaboration API. As mentioned
earlier, at the time of writing this is only possible if you are using Windows Vista or Windows 7.
You can use the classes in this namespace to interact with peers and applications in a number of ways, including
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Signing in and signing out
Discovering peers
Managing contacts and detecting peer presence
You can also use the classes in this namespace to invite other users to join an application, and to exchange
data between users and applications. However, to do this you need to create your own PNM-capable applications,
which is beyond the scope of this chapter.
In the following sections, all the types referred to come from the System.Net.PeerToPeer.Collaboration
namespace unless otherwise specified.
signing in and signing out
One of the most important classes in the System.Net.PeerToPeer.Collaboration namespace is the
PeerCollaboration class. This is a static class that exposes numerous static methods that you can use
for various purposes, as you will see in this and subsequent sections. You can use two of the methods
it exposes, SignIn() and SignOut(), to (unsurprisingly) sign in and sign out of the People Near Me
service. Both of these methods take a single parameter of type PeerScope, which can be one of the
following values:
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PeerScope.None — If you use this value, SignIn() and SignOut() will have no effect.
PeerScope.NearMe — This will sign you in to or out of the link local clouds.
PeerScope.Internet — This will sign you in to or out of the global cloud (which may be necessary
to connect to a contact who is not currently on your local subnet).
PeerScope.All — This will sign you in to or out of all available clouds.
If necessary, calling SignIn() will cause the People Near Me configuration dialog to be displayed.
When a peer is signed in you can use the PeerCollaboration.LocalPresenceInfo property to a value
of type PeerPresenceInfo. This enables standard IM functionality, such as setting your status to away.
You can set the PeerPresenceInfo.DescriptiveText property to a Unicode string of up to 255 characters,
and the PeerPresenceInfo.PresenceStatus property to a value from the PeerPresenceStatus
enumeration. The values that you can use for this enumeration are as follows:
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PeerPresenceStatus.Away — The peer is away.
PeerPresenceStatus.BeRightBack — The peer is away, but will be back soon.
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