Remoting获取客户端的外网IP地址

其实在服务端Remoting可以像读取一个变量一样来获取到连接过来的客户端的IP，不过这个IP不是太容易的取到。

网上有一个解决方案就是使用配置文件来吸取IP地址，但是这个方案需要我们使用配置文件来使用Remoting，如果我们是代码形式的程序，那么怎样获取客户端IP呢。

Remoting、WebService底层都是用Socket来实现，Socket本身很容易的可以获取到IP地址，所以理论上Remoting获取客户端IP是通过的。

我们可以从吸取器入手来获取，假如我们使用TCP通道来通信，在服务端使用TcpServerChannel类，该类其实已支持了吸取器，构造函数如下：

public TcpServerChannel(string name, int port, IServerChannelSinkProvider sinkProvider);

TcpServerChannel类默认的吸取器是BinaryServerFormatterSinkProvider，而吸取器可以设置链表上的下一个吸取器，然后依次执行每一个吸取器。

我们可以得到如下的代码：

IServerChannelSinkProvider serverSink = new ClientIPServerSinkProvider();
BinaryServerFormatterSinkProvider firstSink = new BinaryServerFormatterSinkProvider();
firstSink.Next = serverSink;
TcpServerChannel channel = new TcpServerChannel("tcpserver", port, firstSink);
ChannelServices.RegisterChannel(channel, true);
RemotingConfiguration.RegisterWellKnownServiceType(typeof(RemotableClass), "RemotableClass", WellKnownObjectMode.Singleton);

到这里，如果定义好了RemotableClass类，那么就可以直接取IP地址了：

	public class RemotableClass : MarshalByRefObject
	{
		protected string getIPAddress()
		{
			System.Net.IPAddress ip = System.Runtime.Remoting.Messaging.CallContext.GetData("ClientIPAddress") as System.Net.IPAddress;
			if (ip != null)
			{
				return ip.ToString();
			}
			return null;
		}
	}

如果不知道吸取器的代码，可以参考如下：

	public class ClientIPServerSinkProvider : IServerChannelSinkProvider
	{
		private IServerChannelSinkProvider next = null;

		public ClientIPServerSinkProvider()
		{
		}

		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(IServerResponseChannelSinkStack sinkStack, Object state, IMessage msg, ITransportHeaders headers, Stream stream)
		{
		}

		public Stream GetResponseStream(IServerResponseChannelSinkStack sinkStack, Object state, IMessage msg, ITransportHeaders headers)
		{
			return null;
		}

		public System.Runtime.Remoting.Channels.ServerProcessing ProcessMessage(IServerChannelSinkStack sinkStack, IMessage requestMsg, ITransportHeaders requestHeaders, Stream requestStream, out IMessage responseMsg, out ITransportHeaders responseHeaders, out Stream responseStream)
		{
			if (_next != null)
			{
				IPAddress ip = requestHeaders[CommonTransportKeys.IPAddress] as IPAddress;
				CallContext.SetData("ClientIPAddress", ip);
				return _next.ProcessMessage(sinkStack, requestMsg, requestHeaders, requestStream, out responseMsg, out responseHeaders, out responseStream);
			}
			else
			{
				responseMsg = null;
				responseHeaders = null;
				responseStream = null;

				return ServerProcessing.Complete;
			}
		}

		public IServerChannelSink NextChannelSink
		{
			get
			{
				return _next;
			}
			set
			{
				_next = value;
			}
		}
	}

到这里就完成了。