In my networking class this term, we built a simple chat program. It’s nothing fancy – type in your name, a server, and see what others are posting.

I decided to learn a little bit about .NET Remoting in this exercise. I found numerous examples (including some chat programs) demonstrating how easy it was to create such a program and felt confident with choice I had made. The only thing I had to add to the consolidation of information I had found was a way to select the server one was using.

Yeah… just that.

Now, it’s entirely possible that I missed some nugget of information out there and even that there is a different (better?) way of doing this, but I think I learned something of value through this exercise.

First, the app.config file I was using that worked fine was as follows:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.runtime.remoting>
    <application>
      <client>
        <wellknown
          url=http://ServerName:7777/LeChat
          type="LeChat.Broker.LeChatBroker, LeChatBroker"
        />
      </client>
      <channels>
        <channel
          ref="http"
          name="client"
          port="8888"
        >
          <clientProviders>
            <formatter ref="soap" />
          </clientProviders>
          <serverProviders>
            <formatter ref="soap" typeFilterLevel="Full" />
          </serverProviders>
        </channel>
      </channels>
    </application>
  </system.runtime.remoting>
</configuration>

With this file, one only has to load the settings with:

RemotingConfiguration.Configure( "AppName.exe.config" );

Easy! Of course, if I want to change the name of my server, what do I do?

Some of the learning I had:

The app.config file is meant to be a quasi-read-only file. Although one can write to it through various means, it is loaded at the launch of the application and cached for use throughout the activation – once the program is running, changing the app.config would make no difference.

All of the examples I found for loading the configuration in code were nearly identical:

HttpChannel channel = new HttpChannel( 8888 );
ChannelServices.RegisterChannel( channel );
RemotingConfiguration.RegisterWellKnownServiceType(
      typeof( LeChat.Broker.LeChatBroker ),
      "http://" + serverName + ":7777/LeChat",
      WellKnownObjectMode.Singleton );

This did not provide all of the parameters needed to make the two-way communication possible between the client and the server. In fact, kept going back and forth between having the chat text show up only on the server, or only on the client – depending on whether I registered a … ServiceType, or a … ClientType. Aarrrggghhh!

Finally, I started looking at the overridden constructor on the HttpChannel. I saw something about a IDictionary of ‘properties’ and realized I might be on to something. I started reading about SinkProvider’s and felt even closer. Finally, I had constructed the complete block of code that allowed my little chat program to work and I could insert any server name I needed to:

IDictionary configurationProperties = new Hashtable();
IDictionary serverSinkProviderProperties = new Hashtable();
configurationProperties.Add( "ref", "http" );
configurationProperties.Add( "name", "client" );
configurationProperties.Add( "port", "0" );
serverSinkProviderProperties.Add( "ref", "soap" );
serverSinkProviderProperties.Add( "typeFilterLevel", "Full" );
SoapClientFormatterSinkProvider clientSinkProvider =
      new SoapClientFormatterSinkProvider();
SoapServerFormatterSinkProvider serverSinkProvider =
      new SoapServerFormatterSinkProvider(
        serverSinkProviderProperties, null );
HttpChannel channel = new HttpChannel(
      configurationProperties,
      clientSinkProvider,
      serverSinkProvider );
ChannelServices.RegisterChannel( channel );
RemotingConfiguration.RegisterWellKnownClientType(
      typeof( LeChat.Broker.LeChatBroker ),
      "http://" + serverName + ":7777/LeChat" );

This turned out to be a more substantial investment than I had expected. I did get a chance to learn more about how this stuff works and I’m looking forward to reading Ingo Rammer’s book " Advanced .NET Remoting" to learn more. However, I felt compelled to document what I did so that I can re-learn it all if needed.