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.NET Remoting Message Redirection Channel Sinks

, 20 Jun 2003
An upper logic layer transparent way to redirect .NET remoting calls, enabling exposure of .NET remoting services behind firewall/NAT, to anywhere.
using System;
using System.Collections;
using System.IO;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Security.Principal;
using System.Runtime.Remoting.Messaging;
using System.Threading;

namespace Reachability
{
	
	class Semaphore 
	{
		public Semaphore(int maxCount) 
		{
			_maxCount = maxCount;
			_currentCount = 0;
		}

		public void Acquire() 
		{
			lock(this) 
			{
				while (_currentCount >= _maxCount) 
				{
					Monitor.Wait(this, System.TimeSpan.FromSeconds(60));
				}
				++_currentCount;
			}
		}

		public void Release() 
		{
			lock(this) 
			{
				_currentCount--;
				Monitor.PulseAll(this);
			}

		}

		private int _maxCount;
		private int _currentCount;
	}

	public class SyncQueue : Queue
	{
		Semaphore sem;

		public SyncQueue()
		{ 
			sem = new Semaphore(0);
		}

		public override void Enqueue(object obj)
		{
			base.Enqueue(obj);
			sem.Release();
		}

		public override object Dequeue()
		{
			sem.Acquire();
			return base.Dequeue();
		}
	}

	public class Redirector : MarshalByRefObject
	{
		public Redirector()
		{
		}
		public void GetNextRequest(Guid slot, out Message m)
		{
			SyncQueue q = reqs[slot] as SyncQueue;			
			if(q==null)reqs.Add(slot, q=new SyncQueue());
			m = q.Dequeue() as Message;
		}
		public void ReturnResponse(Guid slot, Response r)
		{
			SyncQueue q = resps[slot] as SyncQueue;			
			if(q==null)resps.Add(slot, q=new SyncQueue());
			q.Enqueue(r);
		}
		[Serializable]
		public class Message
		{
			public bool oneway;
			public ITransportHeaders requestHeaders;
			public byte[] requestStream;
			public IPrincipal callerPrincipal;
			public Message(ITransportHeaders requestHeaders, byte[] requestStream, IPrincipal principal, bool oneway)
			{
				this.oneway=oneway;
				this.requestHeaders=requestHeaders;
				this.requestStream=requestStream;
				this.callerPrincipal=principal;
			}
		}
		[Serializable]
		public class Response
		{
			public Response(ITransportHeaders h, Stream s)
			{
				this.responseHeaders=h;
				responseStream = new byte[s.Length];
				s.Read(responseStream, 0, responseStream.Length);
			}
			public ITransportHeaders responseHeaders;
			public byte[] responseStream;
		}
		Hashtable reqs = Hashtable.Synchronized(new Hashtable());
		Hashtable resps = Hashtable.Synchronized(new Hashtable());
		// no longer listening incoming requests.
		public void RevokeDestinationSlot(Guid slot)
		{
			SyncQueue q = reqs[slot] as SyncQueue;	
			q.Enqueue(new object());

			reqs.Remove(slot);
			resps.Remove(slot);
		}
		public void RedirectRequest(Guid slot, bool oneway, ITransportHeaders requestHeaders, byte[] requestStream, out ITransportHeaders responseHeaders, out byte[] responseStream)
		{
			SyncQueue q = reqs[slot] as SyncQueue;		
			if(q==null)reqs.Add(slot, q=new SyncQueue());
			q.Enqueue(new Message(requestHeaders, requestStream, Thread.CurrentPrincipal, oneway));
			
			if(!oneway)
			{
				q = resps[slot] as SyncQueue;			
				if(q==null)resps.Add(slot, q=new SyncQueue());

				Response r = q.Dequeue() as Response;
				responseHeaders = r.responseHeaders;
				responseStream = r.responseStream;
			}
			else
			{
				responseHeaders = null;
				responseStream = null;
			}
		}
	}
}

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About the Author

zhi
Researcher
United States United States
My name is Zhiheng Cao. I major in Eletronics Engineering, in University of Tokyo. I do part time jobs of computer programming and teaching high school students English and Mathematics.

CodeProject provided me with valuable information for my programming job many times in the past. I hope I can do my part by providing goodies I have.


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