In short, the Remoting Server can make use of Sink and Sink Provider to retrieve the IP address of the incoming request. The IP address is available in the Transport Headers of the incoming message. After retrieving the IP address in the Sink, we save the IP address to the CallContext, so that it will be available later in the code execution path as well. The followings are some background information regarding the topics:


Sinks and Sink Chains
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconsinkssinkchains.asp

Using CallContext
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconusingcallcontext.asp


Code modified from the sample by Ingo Rammer, author of “Advanced .Net Remoting”:


using System;

using System.Collections;

using System.IO;

using System.Runtime.Remoting;

using System.Runtime.Remoting.Messaging ;

using System.Runtime.Remoting.Channels;

using System.Threading;

using System.Net;



namespace ClassLibRemotingIPSink

{



public class ClientIPServerSinkProvider: IServerChannelSinkProvider

{

private IServerChannelSinkProvider next = null;



public ClientIPServerSinkProvider(IDictionary properties, ICollection providerData)

{

}



public void GetChannelData (IChannelDataStore channelData)

{

}



public IServerChannelSink CreateSink (IChannelReceiver channel)

{

IServerChannelSink nextSink = null;

if (next != null)

{

nextSink = next.CreateSink(channel);

}

return new ClientIPServerSink(nextSink);

}



public IServerChannelSinkProvider Next

{

get { return next; }

set { next = value; }

}

}



public class ClientIPServerSink : BaseChannelObjectWithProperties, IServerChannelSink, IChannelSinkBase

{

private IServerChannelSink _next;



public ClientIPServerSink (IServerChannelSink next)

{

_next = next;

}



public void AsyncProcessResponse ( System.Runtime.Remoting.Channels.IServerResponseChannelSinkStack sinkStack , System.Object state , System.Runtime.Remoting.Messaging.IMessage msg , System.Runtime.Remoting.Channels.ITransportHeaders headers , System.IO.Stream stream )

{

}



public Stream GetResponseStream ( System.Runtime.Remoting.Channels.IServerResponseChannelSinkStack sinkStack , System.Object state , System.Runtime.Remoting.Messaging.IMessage msg , System.Runtime.Remoting.Channels.ITransportHeaders headers )

{

return null;

}



public System.Runtime.Remoting.Channels.ServerProcessing ProcessMessage(System.Runtime.Remoting.Channels.IServerChannelSinkStack sinkStack, System.Runtime.Remoting.Messaging.IMessage requestMsg, System.Runtime.Remoting.Channels.ITransportHeaders requestHeaders, System.IO.Stream requestStream, out System.Runtime.Remoting.Messaging.IMessage responseMsg, out System.Runtime.Remoting.Channels.ITransportHeaders responseHeaders, out System.IO.Stream responseStream)

{

if (_next != null)

{

IPAddress ip = requestHeaders[CommonTransportKeys.IPAddress] as IP