Peer Channel Team Blog : Peer Channel Basics: For the Beginner

New to WCF programming??

peerchan — Fri, 25 Jan 2008 04:21:00 GMT

Check out Clemens Vasters' paper introducing WCF up on http://msdn2.microsoft.com/en-us/library/aa480190.aspx...

Also, some presentations and hands-on labs at http://www.dotnet-university.com/CourseMaterials.aspx

-shalini.

Configuring Peer Channel: With/Without App.config

peerchan — Thu, 24 Jan 2008 01:44:00 GMT

So now that we know what the NetPeerTcpBinding is how you can end up using Peer Channel in your standard WCF application, let's take a look at how to configure peer channel. We follow the standard WCF (.NET really) pattern of allowing configuration through an App.config file for your application or imperatively within the code itself. Which way you choose to go really depends on your needs - if you expect your endpoints/configuration to change a lot and want that aspect flexible etc(eg you use a customResolver for discovery and expect to move it around etc) you'd want to minimize code changes and prefer to change these settings in your config file directly. On the other hand, if you dont really expect to modify your source code that often and dont really want an App.config file, you can opt to just configure everything in code itself. Peer Channel (NetPeerTcpbinding) supports both, to provide a programming model consistent with the rest of WCF.

Using App.config:

The following example attempts to configure a Peer Channel endpoint, with endpointAddress = "net.p2p://ChatMesh/chat"; other endpoint information also is added to the endpoint section of the config file, including fully qualified contract type that is associated with the endpoint, name of config file section that configures the specific binding used, and of course also the type of the binding being used.

All binding configuration (in our case, peer channel (NetPeerTcpbinding)-specific ) settings are in the configuration section corresponding to the one specified in the endpoint section above. (Note: Just in case you are wondering, Visual Studio 8 comes preconfigured with xml information for ServiceModel so intellisense would work and you dont really have to know before hand all the various properties etc.. a quick way to confirm is to check your schema file from the VS install here: C:\Program Files\Microsoft Visual Studio 9.0\Xml\Schemas\DotNetConfig.xsd and search for serviceModel definitions..)

In the bindings section of serviceModel configuration, we specify settings for NetPeerTcpBinding as i show below.

<?xml version="1.0" encoding="utf-8" ?>

<system.serviceModel>

<endpoint name="PeerEndpoint"

address="net.p2p://ChatMesh/chat"

binding="netPeerTcpBinding"

bindingConfiguration="PeerBinding"

contract="Microsoft.ServiceModel.Samples.IChat">

</endpoint>

</client>

</binding>

</netPeerTcpBinding>

</bindings>

</system.serviceModel>

</configuration>

It all comes together when in the code, you specify the endpoint name from the config file to the CreateChannel constructor, like so:

// Construct InstanceContext to handle messages on callback interface.

// An instance of ChatApp is created and passed to the InstanceContext.

InstanceContext site = new InstanceContext(new ChatApp());

// Create the participant with the given endpoint configuration. Each participant opens a duplex channel to the mesh. Participant is an instance of the chat application that has opened a channel to the mesh

ChannelFactory<IChatChannel> factory = new DuplexChannelFactory<IChatChannel>(site, "PeerEndpoint");

Note: Notice that the above example assumes that you are creating a duplexChannel for your application and the client itself is the sender/receiver. You can certainly choose to configure your application such that instead of a duplex channel, you have 1 separate sender and multiple clients (receivers). Check out the Default sample for an idea on how to configure the service/client separately in such a case.

Imperative configuration (Via code and not through the App.config file):

The same configuration above can be achieved through setting the properties on NetPeerTcpbinding programmatically. So programmatically, the settings above would look as under:

InstanceContext site = new InstanceContext(new ChatApp());

NetPeerTcpBinding peerBinding = new NetPeerTcpBinding();

peerBinding.Security.Mode = SecurityMode.None;

ChannelFactory<IChatChannel> factory = new DuplexChannelFactory<IChatChannel>(site, peerBinding);

That's all there is to it :)- (unless of course you would like to use the default custom resolver, in which case check out the scenario sample on msdn on what properties to configure). Hopefully this will help answer some common questions around configuration and also how to convert your app from using App.config to pure code.

As always, feedback welcome and appreciated :)..

-shalini.

Getting started- A Fresh look at Peer Channel (NetPeerTcpBinding)

peerchan — Sat, 15 Dec 2007 03:21:00 GMT

Allright, the general consensus amongst new adopters/potential customers seems to be, that our documentation on msdn seems to be not all that crystal-clear, especially for a new comer, to Peer Channel. And that uptil now, we have been targetting advanced scenarios in our blog - Since it might take a while for us to get stuff added/edited up on msdn, we decided to get some basic stuff up on the blog. So, now shall follow some posts about Peer Channel basics - hopefully, from what i think is scratch :).Feel free to comment on the topics covered and on topics you would like covered here in this section..

Where you will find us:

Peer Channel is enabled by default on Windows Vista - as is all of WCF. So you no longer have to download the runtime components (primarily System.ServiceModel.dll) separately or enable it explicitly.

So all you really need to get started is to add references to System.ServiceModel.dll in your project & you should have access to our classes.

What are we (in terms of WCF):

We are essentially a virtual WCF channel - an abstraction built on top of the WCF TCP channel that provides a means for peer-peer communication, without the application having to worry about it. Most of this functionality is exposed to a WCF application through the NetPeerTcpBinding. It is through the NetPeerTcpBinding that you can configure and query static and instance properties like, IsPnrpAvailable, regular properties that can be set on any WCF binding (eg timeouts), and peer-channel specific properties like Resolver (name resolution), Security options etc..

Default behavior/Properties:

(a) Name Resolution: Our default peer name resolution mechanism uses a resolver based on PNRP the PnrpResolver. This is available on XPSP2 (with Networking pack installed) and by default on Windows Vista. Incase, you dont wish to use Pnrp, you have two other options -

i) DefaultCustomResolver: a WCF TCP service-based name resolver; an implementation we provide out-of-the-box. All you need to do is configure the Resolver property on the NetPeerTcpbinding instance. There are some more configuration steps and our scenario sample on msdn shows how to configure your app to use this resolver.

ii) Custom Resolver - There are times where you might to use your own discovery resolver - for this you can plug in your custom name resolver again by specifying the NetPeerTcpBinding's resolver property with the type of your resolver class. We also ship a custom resolver implementation (again TCP-based) sample for reference.

(b) Security: By default, Peer channel uses password-based authentication for communication amongst peers. So make sure to configure your password on the instance of channelFactory through teh Credential.Peer.MeshPassword property. The certificates used in this authentication are auto-generated and need not be generated/set explicitly, but your application can do so using the Credential.Peer.Certificate property. Our samples show best how this and other security modes can be used with Peer Channel. We'll also cover more on this in a later post..

(c) Listen port: Ports on which your node is listening are auto-generated. So it is really simple for you to run multiple instances of your application on the same machine without any configuration changes. If you would like to explicitly set the port your application should listen on, use the Port property on the netPeerTcpBinding instance.

(d) Listen IPAddress: By default, Peer Channel uses all available IPv4/IPv6 addresses to bind to (including link-local/global IPv6 addresses). However, if you choose, you can make it listen on specific IP addresses using the ListenIPAddress property on binding instance.

Hopefully, I've covered some basics, and this post, coupled with the samples on msdn, should help you get started with writing your first Peer Channel app :). Stay tuned for more fun stuff :)