From 70d9aebc9d9c9d90383c32a67ef4ad8f9772d26a Mon Sep 17 00:00:00 2001
From: Darren Horrocks <killallthehumans@gmail.com>
Date: Sat, 22 Nov 2014 13:45:09 +0000
Subject: [PATCH] local peer discovery

---
 LocalPeerDiscovery.cs | 97 ++++++++++++++++++++++++++++++++++++-------
 README.md             |  8 ++--
 2 files changed, 85 insertions(+), 20 deletions(-)

diff --git a/LocalPeerDiscovery.cs b/LocalPeerDiscovery.cs
index d5b097e..bf1da3f 100644
--- a/LocalPeerDiscovery.cs
+++ b/LocalPeerDiscovery.cs
@@ -1,4 +1,5 @@
-using System.Net.Sockets;
+using System.Diagnostics;
+using System.Net.Sockets;
 using System.Text;
 using System.Threading;
 
@@ -10,57 +11,105 @@ public class LocalPeerDiscovery
 		private const int lpdMulticastPort = 6771;
 
 		private readonly Socket udpReaderSocket;
+		private readonly Socket udpSenderSocket;
 
 		private Thread thread;
 		private bool _killSwitch;
 
 		public delegate void NewPeerCB(IPAddress address, int port, String infoHash);
-
 		public event NewPeerCB NewPeer;
 
+		private int ttl = 8;
+
+		public int TTL
+		{
+			get { return ttl; }
+			set
+			{
+				ttl = value;
+
+				udpSenderSocket.SetSocketOption(SocketOptionLevel.IP,
+				SocketOptionName.MulticastTimeToLive,
+				ttl);
+			}
+		}
+
 		public LocalPeerDiscovery()
 		{
 			udpReaderSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
+			udpSenderSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
 		}
 
-		public LocalPeerDiscovery(Socket socket)
+		public LocalPeerDiscovery(Socket receive, Socket send)
+		{
+			ValidateSocket(receive, "receive");
+			ValidateSocket(send, "send");
+
+			udpReaderSocket = receive;
+			udpSenderSocket = send;
+		}
+
+		[DebuggerHidden, DebuggerStepThrough]
+		private void ValidateSocket(Socket socket, String name)
 		{
 			if (socket == null)
 			{
-				throw new ArgumentNullException("socket");
+				throw new ArgumentNullException(name);
 			}
 
 			if (socket.ProtocolType != ProtocolType.Udp)
 			{
-				throw new ArgumentException("socket must be a UDP socket", "socket");
+				throw new ArgumentException("socket must be a UDP socket", name);
 			}
 
 			if (socket.SocketType != SocketType.Dgram)
 			{
-				throw new ArgumentException("socket must be a datagram socket", "socket");
+				throw new ArgumentException("socket must be a datagram socket", name);
 			}
-
-			udpReaderSocket = socket;
 		}
 
 		public void Open()
 		{
+			IPAddress address = IPAddress.Parse(lpdMulticastAddress);
+			SetupReaderSocket(address, lpdMulticastPort);
+			SetupSenderSocket(address, lpdMulticastPort);
+
+			thread = new Thread(Process);
+			thread.Start();
+		}
+
+		private void SetupReaderSocket(IPAddress address, int port)
+		{
+			var endPoint = new IPEndPoint(IPAddress.Any, port);
+
 			udpReaderSocket.ExclusiveAddressUse = false;
 			udpReaderSocket.SetSocketOption(SocketOptionLevel.Socket,
 				SocketOptionName.ReuseAddress,
 				true);
 
-			IPAddress address = IPAddress.Parse(lpdMulticastAddress);
-
-			var endPoint = new IPEndPoint(IPAddress.Any, lpdMulticastPort);
 			udpReaderSocket.Bind(endPoint);
 
-			udpReaderSocket.SetSocketOption(SocketOptionLevel.IP, 
-				SocketOptionName.AddMembership, 
+			udpReaderSocket.SetSocketOption(SocketOptionLevel.IP,
+				SocketOptionName.AddMembership,
 				new MulticastOption(address, IPAddress.Any));
+		}
 
-			thread = new Thread(Process);
-			thread.Start();
+		private void SetupSenderSocket(IPAddress address, int port)
+		{
+			var endPoint = new IPEndPoint(address, port);
+
+			udpReaderSocket.ExclusiveAddressUse = false;
+			udpReaderSocket.SetSocketOption(SocketOptionLevel.Socket,
+				SocketOptionName.ReuseAddress,
+				true);
+			udpSenderSocket.SetSocketOption(SocketOptionLevel.IP, 
+				SocketOptionName.AddMembership, 
+				new MulticastOption(address));
+			udpSenderSocket.SetSocketOption(SocketOptionLevel.IP, 
+				SocketOptionName.MulticastTimeToLive, 
+				TTL);
+
+			udpSenderSocket.Connect(endPoint);
 		}
 
 		public void Close()
@@ -69,6 +118,7 @@ public void Close()
 			thread.Abort();
 
 			udpReaderSocket.Close();
+			udpSenderSocket.Close();
 		}
 
 		private void Process()
@@ -114,5 +164,22 @@ private void Process()
 				}
 			}
 		}
+
+		public void Announce(int listeningPort, String infoHash)
+		{
+			String message = String.Format("BT-SEARCH * HTTP/1.1\r\n" +
+			                               "Host: {2}:{3}\r\n" +
+			                               "Port: {0}\r\n" +
+			                               "Infohash: {1}\r\n" +
+			                               "\r\n\r\n", 
+										   listeningPort, 
+										   infoHash,
+										   lpdMulticastAddress,
+										   lpdMulticastPort);
+
+			byte[] buffer = Encoding.ASCII.GetBytes(message);
+
+			udpSenderSocket.Send(buffer);
+		}
 	}
 }
diff --git a/README.md b/README.md
index 3fff936..6f7dc26 100644
--- a/README.md
+++ b/README.md
@@ -3,10 +3,8 @@ System.Net.Torrent
 
 Open source bittorrent scraper and peer wire implementation written in C#
 
-- [x] UDP Announce
-- [x] UDP Scrape
-- [x] HTTP Announce
-- [x] HTTP Scrape
+- [x] Tracker Announce (HTTP/UDP)
+- [x] Tracker Scrape (HTTP/UDP)
 - [x] PeerWire (TCP) Client
 - [x] Choke
 - [x] Unchoke
@@ -18,6 +16,6 @@ Open source bittorrent scraper and peer wire implementation written in C#
 - [x] Piece
 - [x] Fast Protocol Extensions
 - [x] Extended Protocol Extensions
-- [ ] Local Peer Discovery
+- [x] Local Peer Discovery (Non-existant Multicast BEP-14)
 - [x] Peer Exchange (utPEX)
 - [x] Trackerless Metadata (utMetadata)
\ No newline at end of file