Building a Basic .NET Remoting Application 之二 Building a Host Application

Building a Host Application

By itself, the

RemotableType

class defined in the Building a Remotable Type topic is not special. To enable objects in other application domains to create instances of this object remotely, you must build a host or listener application to do two things:

Choose and register a channel, which is an object that handles the networking protocols and serialization formats on your behalf.
Register your type with the .NET remoting system so that it can use your channel to listen for requests for your type.

The .NET Framework includes two default channels, HttpChannel (which uses SOAP formatting) and TcpChannel (which uses binary formatting). HttpChannel is a good channel to start with because in some scenarios it can be used through firewalls without opening a port, and it supports standard security and authentication protocols. For more information about choosing channels that suit your scenario, see Channels.

You can build listener applications using any type of application domain — a Windows Forms application, an ASP.NET Web application, a console application, a Windows Service (also known as a Windows NT Service), or any other managed application domain. Because remote configuration is done on a per-application-domain basis, the application domain must be running to listen for requests.


Configuration can be done programmatically or by using an application or machine configuration file. The following code implements a simple

RemotableType

host application domain that uses a configuration file. (Using a configuration file enables you to change the remoting configuration without recompiling your executable, among other things.) For details on the configuration of the .NET remoting infrastructure, see Configuration.

[C#]
// Listener.cs
using System;
using System.Runtime.Remoting;

public class Listener{
public static void Main(){
RemotingConfiguration.Configure("Listener.exe.config");
Console.WriteLine("Listening for requests. Press Enter to exit...");
Console.ReadLine();
}
}

To compile this class into a host or listener executable using the command-line tools that ship with the .NET Framework SDK, save it as

Listener

.language-extension (or use another file name of your choice, where the language extension is the language you want to compile). Save the file in the same directory in which you saved the

RemotableType.dll

that you built in the Building a Remotable Typetopic. At the command prompt in that directory, type the following command:

[C#]

csc /noconfig /r:RemotableType.dll Listener.cs

In this example, the file name is:

[C#]
Listener.cs

The

Listener

class must be able to find the

Listener.exe.config

file to load the configuration for the

RemotableType

class. This configuration file should be saved in the same directory as

Listener.exe

, or it will not be found and an exception will be thrown. The following code shows the

Listener.exe.config

configuration file for this listening or host application domain.

<configuration>
<system.runtime.remoting>
<application>
<service>
<wellknown
mode="Singleton"
type="RemotableType, RemotableType"
objectUri="RemotableType.rem"
/>
</service>
<channels>
<channel ref="http" port="8989"/>
</channels>
</application>
</system.runtime.remoting>
</configuration>

The remoting system uses the information in this file to listen for and route remote requests to an instance of a remotable type. The file specifies the Singleton server-activation mode, the type name and assembly of the type on behalf of which it is to listen, and the object Uniform Resource Identifier (URI) or external name of the object. (For more details about object URIs and remoting, see Activation URLs.) The file also tells the remoting system to listen for requests on port 8989 using the system-provided HttpChannel.