Internet Magic (Proxy Server) Windows Application

using System;
using System.Net;
using System.Net.Sockets;
using System.Collections;
using IPNumbers;
using System.Windows.Forms;

namespace internet_magic {

///<summary>Specifies the basic methods and properties of a <c>Listener</c> object. This is an abstract class and must be inherited.</summary>
///<remarks>The Listener class provides an abstract base class that represents a listening socket of the proxy server. Descendant classes further specify the protocol that is used between those two connections.</remarks>
public abstract class Listener : IDisposable{
	///<summary>Initializes a new instance of the Listener class.</summary>
	///<param name="Port">The port to listen on.</param>
	///<param name="Address">The address to listen on. You can specify IPAddress.Any to listen on all installed network cards.</param>
	///<remarks>For the security of your server, try to avoid to listen on every network card (IPAddress.Any). Listening on a local IP address is usually sufficient and much more secure.</remarks>
    public Listener (int Port, IPAddress Address){
		this.Port = Port;
		this.Address = Address;
	}
    
	///<summary>Gets or sets the port number on which to listen on.</summary>
	///<value>An integer defining the port number to listen on.</value>
	///<seealso cref ="Address"/>
	///<exception cref="ArgumentException">The specified value is less than or equal to zero.</exception>
	protected int Port {
		get {
			return m_Port;
		}
		set {
			if (value <= 0) 
				throw new ArgumentException();
			m_Port = value;
			Restart();
		}
	}
	///<summary>Gets or sets the address on which to listen on.</summary>
	///<value>An IPAddress instance defining the IP address to listen on.</value>
	///<seealso cref ="Port"/>
	///<exception cref="ArgumentNullException">The specified value is null.</exception>
	protected IPAddress Address {
		get {
			return m_Address;
		}
		set {
			if (value == null)
				throw new ArgumentNullException();
			m_Address = value;
			Restart();
		}
	}
	///<summary>Gets or sets the listening Socket.</summary>
	///<value>An instance of the Socket class that's used to listen for incoming connections.</value>
	///<exception cref="ArgumentNullException">The specified value is null.</exception>
	protected Socket ListenSocket {
		get {
			return m_ListenSocket;
		}
		set {
			if (value == null)
				throw new ArgumentNullException();
			m_ListenSocket = value;
		}
	}
	///<summary>Gets the list of connected clients.</summary>
	///<value>An instance of the ArrayList class that's used to store all the connections.</value>
	protected ArrayList Clients {
		get {
			return m_Clients;
		}
	}
	///<summary>Gets a value indicating whether the Listener has been disposed or not.</summary>
	///<value>An boolean that specifies whether the object has been disposed or not.</value>
	public bool IsDisposed {
		get {
			return m_IsDisposed;
		}
	}
	///<summary>Starts listening on the selected IP address and port.</summary>
	///<exception cref="SocketException">There was an error while creating the listening socket.</exception>
	public void Start() {
		try {
            ListenSocket = new Socket(Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
            ListenSocket.Bind(new IPEndPoint(Address, Port));
			ListenSocket.Listen(50);
            ListenSocket.BeginAccept(new AsyncCallback(this.OnAccept), ListenSocket);
            //ListenSocket.Close();
		} catch {
			ListenSocket = null;
			throw new SocketException();
		}
	}
	///<summary>Restarts listening on the selected IP address and port.</summary>
	///<remarks>This method is automatically called when the listening port or the listening IP address are changed.</remarks>
	///<exception cref="SocketException">There was an error while creating the listening socket.</exception>
	protected void Restart() {
		//If we weren't listening, do nothing
		if (ListenSocket == null)
			return;
        
		ListenSocket.Close();
        
		Start();
	}
    
   
	///<summary>Adds the specified Client to the client list.</summary>
	///<remarks>A client will never be added twice to the list.</remarks>
	///<param name="client">The client to add to the client list.</param>
	protected void AddClient(Client client) {
		if (Clients.IndexOf(client) == -1)
			Clients.Add(client);
	}
	///<summary>Removes the specified Client from the client list.</summary>
	///<param name="client">The client to remove from the client list.</param>
	protected void RemoveClient(Client client) {
		Clients.Remove(client);
	}
	///<summary>Returns the number of clients in the client list.</summary>
	///<returns>The number of connected clients.</returns>
	public int GetClientCount() {
		return Clients.Count;
	}
	///<summary>Returns the requested client from the client list.</summary>
	///<param name="Index">The index of the requested client.</param>
	///<returns>The requested client.</returns>
	///<remarks>If the specified index is invalid, the GetClientAt method returns null.</remarks>
	public Client GetClientAt(int Index) {
		if (Index < 0 || Index >= GetClientCount())
			return null;
		return (Client)Clients[Index];
	}
	///<summary>Gets a value indicating whether the Listener is currently listening or not.</summary>
	///<value>A boolean that indicates whether the Listener is currently listening or not.</value>
	public bool Listening {
		get {
			return ListenSocket != null;
		}
	}
	///<summary>Disposes of the resources (other than memory) used by the Listener.</summary>
	///<remarks>Stops listening and disposes <em>all</em> the client objects. Once disposed, this object should not be used anymore.</remarks>
	///<seealso cref ="System.IDisposable"/>
	public void Dispose() {
		if (IsDisposed)
			return;
		while (Clients.Count > 0) {
			((Client)Clients[0]).Dispose();
		}
		try {
			ListenSocket.Shutdown(SocketShutdown.Both);
            ListenSocket.Close();
		} catch {}
		if (ListenSocket != null)
			ListenSocket.Close();
		m_IsDisposed = true;
	}
	///<summary>Finalizes the Listener.</summary>
	///<remarks>The destructor calls the Dispose method.</remarks>
	~Listener() {
		Dispose();
	}
	///<summary>Returns an external IP address of this computer, if present.</summary>
	///<returns>Returns an external IP address of this computer; if this computer does not have an external IP address, it returns the first local IP address it can find.</returns>
	///<remarks>If this computer does not have any configured IP address, this method returns the IP address 0.0.0.0.</remarks>
	public static IPAddress GetLocalExternalIP() {
		try {
            IPHostEntry he = Dns.Resolve(Dns.GetHostName());
			for (int Cnt = 0; Cnt < he.AddressList.Length; Cnt++) {
				if (IsRemoteIP(he.AddressList[Cnt]))
					return he.AddressList[Cnt];
			}
			return he.AddressList[0];
		} catch {
			return IPAddress.Any;
		}
	}
	///<summary>Checks whether the specified IP address is a remote IP address or not.</summary>
	///<param name="IP">The IP address to check.</param>
	///<returns>True if the specified IP address is a remote address, false otherwise.</returns>
	protected static bool IsRemoteIP(IPAddress IP) {
        IPList iplist = new IPList(); 
        iplist.AddRange("10.0.0.0", "10.0.255.255");
               
        iplist.AddRange("172.16.0.0", "172.31.255.255");
        
        iplist.AddRange("192.168.0.0", "192.168.255.255");

        return (iplist.CheckNumber(IP.ToString()) && (!IP.Equals(IPAddress.Any)) &&
                (!IP.Equals(IPAddress.Loopback)) && (!IP.Equals(IPAddress.Broadcast)));

		
		//Not 10.x.x.x And Not 172.16.x.x <-> 172.31.x.x And Not 192.168.x.x
		//And Not Any And Not Loopback And Not Broadcast
		
	}
	///<summary>Checks whether the specified IP address is a local IP address or not.</summary>
	///<param name="IP">The IP address to check.</param>
	///<returns>True if the specified IP address is a local address, false otherwise.</returns>
	protected static bool IsLocalIP(IPAddress IP) {
        IPList iplist = new IPList();
        iplist.AddRange("10.0.0.0", "10.0.255.255");

        iplist.AddRange("172.16.0.0", "172.31.255.255");

        iplist.AddRange("192.168.0.0", "192.168.255.255");

        return (iplist.CheckNumber(IP.ToString()) && (!IP.Equals(IPAddress.Any)) &&
                (!IP.Equals(IPAddress.Loopback)) && (!IP.Equals(IPAddress.Broadcast)));

		//10.x.x.x Or 172.16.x.x <-> 172.31.x.x Or 192.168.x.x
		
	}
	///<summary>Returns an internal IP address of this computer, if present.</summary>
	///<returns>Returns an internal IP address of this computer; if this computer does not have an internal IP address, it returns the first local IP address it can find.</returns>
	///<remarks>If this computer does not have any configured IP address, this method returns the IP address 0.0.0.0.</remarks>
	public static IPAddress GetLocalInternalIP() {
		try {
            IPHostEntry he = Dns.Resolve(Dns.GetHostName());
			for (int Cnt = 0; Cnt < he.AddressList.Length; Cnt++) {
				if (IsLocalIP(he.AddressList[Cnt]))
					return he.AddressList[Cnt];
			}
			return he.AddressList[0];
		} catch {
			return IPAddress.Any;
		}
	}
	///<summary>Called when there's an incoming client connection waiting to be accepted.</summary>
	///<param name="ar">The result of the asynchronous operation.</param>
	public abstract void OnAccept(IAsyncResult ar);
    ///<summary>Returns a string representation of this object.</summary>
	///<returns>A string with information about this object.</returns>
	public override abstract string ToString();
	///<summary>Returns a string that holds all the construction information for this object.</summary>
	///<value>A string that holds all the construction information for this object.</value>
	public abstract string ConstructString {get;}

   
	// private variables
	/// <summary>Holds the value of the Port property.</summary>
	private int m_Port;
	/// <summary>Holds the value of the Address property.</summary>
	private IPAddress m_Address;
	/// <summary>Holds the value of the ListenSocket property.</summary>
	private Socket m_ListenSocket;
	/// <summary>Holds the value of the Clients property.</summary>
	private ArrayList m_Clients = new ArrayList();
	/// <summary>Holds the value of the IsDisposed property.</summary>
	private bool m_IsDisposed = false;
    
}

}