diff --git a/OpenRa.FileFormats/Session.cs b/OpenRa.FileFormats/Session.cs
index e378d876e5..1d0ddd45bc 100644
--- a/OpenRa.FileFormats/Session.cs
+++ b/OpenRa.FileFormats/Session.cs
@@ -30,7 +30,7 @@ namespace OpenRa.FileFormats
 		public class Global
 		{
 			public string Map = "scm12ea.ini";
-			public string[] Mods = {};	// filename:sha1 pairs.
+			public string[] Packages = {};	// filename:sha1 pairs.
 			public int OrderLatency = 3;
 		}
 	}
diff --git a/OpenRa.Game/Game.cs b/OpenRa.Game/Game.cs
index 814c9524d1..75a4c7ed86 100644
--- a/OpenRa.Game/Game.cs
+++ b/OpenRa.Game/Game.cs
@@ -382,20 +382,24 @@ namespace OpenRa.Game
 
 			// todo: if we don't have all the resources, we don't want to do this yet.
 
+			if (Game.orderManager.FramesAhead != LobbyInfo.GlobalSettings.OrderLatency
+				&& !Game.orderManager.GameStarted)
+			{
+				Game.orderManager.FramesAhead = LobbyInfo.GlobalSettings.OrderLatency;
+				Game.chat.AddLine(Color.White, "Server",
+					"Order lag is now {0} frames.".F(LobbyInfo.GlobalSettings.OrderLatency));
+			}
+
+			PackageDownloader.SetPackageList(LobbyInfo.GlobalSettings.Packages);
+			if (!PackageDownloader.IsIdle())
+				return;
+
 			if (mapName != LobbyInfo.GlobalSettings.Map)
 			{
 				chat.AddLine(Color.White, "Debug", 
 					"Map change {0} -> {1}".F(mapName, session.GlobalSettings.Map));
 				ChangeMap(LobbyInfo.GlobalSettings.Map);
 			}
-
-			if (Game.orderManager.FramesAhead != LobbyInfo.GlobalSettings.OrderLatency
-				&& !Game.orderManager.GameStarted)
-			{
-				Game.orderManager.FramesAhead = LobbyInfo.GlobalSettings.OrderLatency;
-				Game.chat.AddLine(Color.White, "Server", 
-					"Order lag is now {0} frames.".F(LobbyInfo.GlobalSettings.OrderLatency));
-			}
 		}
 
 		public static void StartGame()
diff --git a/OpenRa.Game/OpenRa.Game.csproj b/OpenRa.Game/OpenRa.Game.csproj
index d3c6ee66cf..f6c2dd173a 100644
--- a/OpenRa.Game/OpenRa.Game.csproj
+++ b/OpenRa.Game/OpenRa.Game.csproj
@@ -117,6 +117,7 @@
     <Compile Include="Orders\SellOrderGenerator.cs" />
     <Compile Include="Orders\ChronoshiftDestinationOrderGenerator.cs" />
     <Compile Include="Ore.cs" />
+    <Compile Include="PackageDownloader.cs" />
     <Compile Include="PathSearch.cs" />
     <Compile Include="ProductionItem.cs" />
     <Compile Include="Orders\ReplayOrderSource.cs" />
diff --git a/OpenRa.Game/Orders/UnitOrders.cs b/OpenRa.Game/Orders/UnitOrders.cs
index 1a23ff7f8e..92c2110aad 100644
--- a/OpenRa.Game/Orders/UnitOrders.cs
+++ b/OpenRa.Game/Orders/UnitOrders.cs
@@ -60,6 +60,11 @@ namespace OpenRa.Game.Orders
 					Game.SyncLobbyInfo(order.TargetString);
 					break;
 				}
+			case "FileChunk":
+				{
+					PackageDownloader.ReceiveChunk(order.TargetString);
+					break;
+				}
 
 			default:
 				{
diff --git a/OpenRa.Game/PackageDownloader.cs b/OpenRa.Game/PackageDownloader.cs
new file mode 100644
index 0000000000..3e79ba3459
--- /dev/null
+++ b/OpenRa.Game/PackageDownloader.cs
@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.FileFormats;
+using System.IO;
+using System.Security.Cryptography;
+
+namespace OpenRa.Game
+{
+	static class PackageDownloader
+	{
+		static string[] allPackages = { };
+		static List<string> missingPackages = new List<string>();
+		static string currentPackage = null;
+		static MemoryStream content = null;
+
+		public static void SetPackageList(string[] packages)
+		{
+			allPackages = packages;
+			missingPackages = allPackages.Where(p => !HavePackage(p)).ToList();
+
+			if (currentPackage == null || !missingPackages.Contains(currentPackage))
+				BeginDownload();
+		}
+
+		public static void ReceiveChunk(string data)
+		{
+			
+		}
+
+		static void BeginDownload()
+		{
+			if (missingPackages.Count == 0)
+			{	// we're finished downloading resources!
+				currentPackage = null;
+				return;
+			}
+
+			currentPackage = missingPackages[0];
+			missingPackages.RemoveAt(0);
+
+			content = new MemoryStream();
+		}
+
+		static void EndDownload()
+		{
+			File.WriteAllBytes(currentPackage.Split(':')[0], content.ToArray());
+			currentPackage = null;
+
+			BeginDownload();
+		}
+
+		public static bool IsIdle()
+		{
+			return currentPackage == null 
+				&& missingPackages.Count == 0;
+		}
+
+		static bool HavePackage(string p)
+		{
+			var parts = p.Split(':');
+			return File.Exists(parts[0]) && CalculateSHA1(parts[0]) == parts[1];
+		}
+
+		public static string CalculateSHA1(string filename)
+		{
+			using (var csp = SHA1.Create())
+				return new string(csp.ComputeHash(File.ReadAllBytes(filename))
+					.SelectMany(a => a.ToString("x2")).ToArray());
+		}
+	}
+}