Implement SRV DNS record lookup for multiplayer server connections

Replace instances of 25565 with ServerItem.DEFAULT_PORT
Add portable static NetworkUtils DNS resolution methods
Use NetworkUtils DNS resolution when polling and connecting to servers

Author: raws

lib/dnsjava-2.1.3.jar

@@ -3,7 +3,9 @@
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.net.InetAddress;
+// Spout start
+import java.net.InetSocketAddress;
+// Spout end
 import java.net.Socket;
 import java.net.URL;
 import java.net.UnknownHostException;
@@ -12,10 +14,15 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
-//Spout start
+
+// Spout start
+import net.minecraft.client.Minecraft;
+
 import org.spoutcraft.client.SpoutClient;
 import org.spoutcraft.client.io.FileDownloadThread;
-//SPout end
+import org.spoutcraft.client.util.NetworkUtils;
+// Spout end
+
 import net.minecraft.client.Minecraft;
 import net.minecraft.src.Block;
 import net.minecraft.src.Chunk;
@@ -138,14 +145,20 @@ public class NetClientHandler extends NetHandler {
 	public List playerNames = new ArrayList();
 	public int currentServerMaxPlayers = 20;
 	Random rand = new Random();
-	//Spout start
+	// Spout start
 	long timeout = System.currentTimeMillis() + 5000;
+	// Spout end
 
 	public NetClientHandler(Minecraft var1, String var2, int var3) throws UnknownHostException, IOException {
 		this.mc = var1;
-		Socket var4 = new Socket(InetAddress.getByName(var2), var3);
-		this.netManager = new NetworkManager(var4, "Client", this);
-		//Spout start
+		
+		// Spout start
+		InetSocketAddress address = NetworkUtils.resolve(var2, var3);
+		if (address.isUnresolved()) {
+			throw new UnknownHostException(address.getHostName());
+		}
+		this.netManager = new NetworkManager(new Socket(address.getAddress(), address.getPort()), "Client", this);
+		
 		org.spoutcraft.client.gui.error.GuiConnectionLost.lastServerIp = var2;
 		org.spoutcraft.client.gui.error.GuiConnectionLost.lastServerPort = var3;
 		//Spout end

src/minecraft/net/minecraft/src/NetClientHandler.java

@@ -27,6 +27,8 @@
 
 import java.lang.String;
 
+import org.spoutcraft.client.gui.server.ServerItem;
+
 import net.minecraft.src.GuiConnecting;
 
 public class ReconnectManager {
@@ -59,7 +61,7 @@ public static void detectKick(String infoString, String reason, Object[] objects
 					}
 				} else if (split.length == 2) {
 					hostName = split[1].trim();
-					portNum = 25565;
+					portNum = ServerItem.DEFAULT_PORT;
 				}
 			}
 		}

src/minecraft/org/spoutcraft/client/ReconnectManager.java

@@ -88,7 +88,7 @@ public void load() {
 					for (HashMap<String, Object> item: list) {
 						String title = "";
 						String ip = "";
-						int port = 25565;
+						int port = ServerItem.DEFAULT_PORT;
 						int databaseId = -1;
 						if (item.containsKey("title")) title = (String) item.get("title");
 						if (item.containsKey("ip")) ip = (String) item.get("ip");
@@ -125,14 +125,14 @@ private void importLegacyTXT() {
 						String title = args[0];
 						String split[] = args[1].split(":");
 						String ip = split[0];
-						int port = split.length > 1 ? Integer.parseInt(split[1]) : 25565;
+						int port = split.length > 1 ? Integer.parseInt(split[1]) : ServerItem.DEFAULT_PORT;
 						addServer(title, ip, port);
 					}
 					if (args.length == 3) {
 						String title = args[1];
 						String split[] = args[0].split(":");
 						String ip = split[0];
-						int port = split.length > 1 ? Integer.parseInt(split[1]) : 25565;
+						int port = split.length > 1 ? Integer.parseInt(split[1]) : ServerItem.DEFAULT_PORT;
 						int databaseId = Integer.parseInt(args[2]);
 						addServer(title, ip, port, databaseId);
 					}

src/minecraft/org/spoutcraft/client/gui/server/FavoritesModel.java

@@ -50,14 +50,14 @@ public class GuiAddFavorite extends GuiScreen {
 
 	public GuiAddFavorite(String server, GuiScreen parent) {
 		String splt[] = server.split(":");
-		int port = 25565;
+		int port = ServerItem.DEFAULT_PORT;
 		if (splt.length > 0) {
 			server = splt[0];
 			if (splt.length > 1) {
 				try {
 					port = Integer.valueOf(splt[1]);
 				} catch (NumberFormatException e) {
-					port = 25565;
+					port = ServerItem.DEFAULT_PORT;
 				}
 			}
 		} else {
@@ -105,7 +105,7 @@ public void initGui() {
 		textIp.setHeight(20);
 		textIp.setX(left).setY(top);
 		getScreen().attachWidget(spoutcraft, textIp);
-		textIp.setText(item.getIp() + (item.getPort()!=25565?":"+item.getPort():""));
+		textIp.setText(item.getIp() + (item.getPort() != ServerItem.DEFAULT_PORT ? ":" + item.getPort() : ""));
 		top+=25;
 
 		buttonClear = new GenericButton("Clear");
@@ -171,7 +171,7 @@ protected void buttonClicked(Button btn) {
 			textIp.setText("");
 			item.setTitle("");
 			item.setIp("");
-			item.setPort(25565);
+			item.setPort(ServerItem.DEFAULT_PORT);
 			updateButtons();
 		}
 	}
@@ -191,7 +191,7 @@ private void updateItem() {
 				item.setPort(Integer.valueOf(split[1]));
 			} catch(Exception e) {
 				// Handles both InvalidNumber and OutOfRange exceptions, yay
-				item.setPort(25565);
+				item.setPort(ServerItem.DEFAULT_PORT);
 			}
 		}
 

src/minecraft/org/spoutcraft/client/gui/server/GuiAddFavorite.java

@@ -228,7 +228,7 @@ public void doQuickJoin() {
 			if (!adress.isEmpty()) {
 				String split[] = adress.split(":");
 				String ip = split[0];
-				int port = split.length > 1 ? Integer.parseInt(split[1]) : 25565;
+				int port = split.length > 1 ? Integer.parseInt(split[1]) : ServerItem.DEFAULT_PORT;
 				SpoutClient.getHandle().gameSettings.lastServer = adress.replace(":", "_");
 				SpoutClient.getHandle().gameSettings.saveOptions();
 				SpoutClient.getInstance().getServerManager().join(ip, port, this, "Favorites");

src/minecraft/org/spoutcraft/client/gui/server/GuiFavorites.java

@@ -135,7 +135,7 @@ protected void createInstances() {
 		labelAccess.setTextColor(new Color(0xffaaaaaa));
 		content.attachWidget(spoutcraft, labelAccess);
 
-		labelAddress = new GenericLabel(item.getIp() + (item.getPort()!=25565?item.getPort():""));
+		labelAddress = new GenericLabel(item.getIp() + (item.getPort() != ServerItem.DEFAULT_PORT ? item.getPort() : ""));
 		labelAddress.setTextColor(new Color(0xffaaaaaa));
 		content.attachWidget(spoutcraft, labelAddress);
 

src/minecraft/org/spoutcraft/client/gui/server/GuiServerInfo.java

@@ -43,6 +43,7 @@
 
 import org.spoutcraft.client.SpoutClient;
 import org.spoutcraft.client.io.MirrorUtils;
+import org.spoutcraft.client.util.NetworkUtils;
 import org.spoutcraft.spoutcraftapi.packet.PacketUtil;
 
 public class PollResult {
@@ -183,7 +184,12 @@ public void run() {
 				long start = System.currentTimeMillis();
 				sock = new Socket();
 				sock.setSoTimeout(10000);
-				sock.connect(new InetSocketAddress(ip, port), 10000);
+				InetSocketAddress address = NetworkUtils.resolve(ip, port);
+				if (address.isUnresolved()) {
+					ping = PING_UNKNOWN;
+					return;
+				}
+				sock.connect(address, 10000);
 				sock.setTcpNoDelay(true);
 				sock.setTrafficClass(18);
 

src/minecraft/org/spoutcraft/client/gui/server/PollResult.java

@@ -43,6 +43,11 @@
 import org.spoutcraft.spoutcraftapi.gui.RenderUtil;
 
 public class ServerItem implements ListWidgetItem {
+	/**
+	 * The default Minecraft server port.
+	 */
+	public static final int DEFAULT_PORT = 25565;
+	
 	protected ListWidget widget;
 
 	protected String ip;
@@ -213,7 +218,7 @@ public void render(int x, int y, int width, int height) {
 		}
 		SpoutClient.getHandle().renderEngine.bindTexture(SpoutClient.getHandle().renderEngine.getTexture("/gui/icons.png"));
 		RenderUtil.drawTexturedModalRectangle(x + width - 2 - 10, y + 2, 0 + xOffset * 10, 176 + yOffset * 8, 10, 8, 0f);
-		if (port != 25565) {
+		if (port != DEFAULT_PORT) {
 			font.drawStringWithShadow(ip + ":" +port, x+marginleft, y+20, 0xaaaaaa);
 		} else {
 			font.drawStringWithShadow(ip, x+marginleft, y+20, 0xaaaaaa);

src/minecraft/org/spoutcraft/client/gui/server/ServerItem.java

@@ -30,10 +30,24 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
 import java.net.URISyntaxException;
 import java.net.URL;
+import java.util.regex.Pattern;
+
+import org.spoutcraft.client.gui.server.ServerItem;
+import org.xbill.DNS.Lookup;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.SRVRecord;
+import org.xbill.DNS.TextParseException;
+import org.xbill.DNS.Type;
 
 public class NetworkUtils {
+	/**
+	 * A {@link Pattern} matching valid DNS hostnames (as opposed to IP addresses).
+	 */
+	private static final Pattern HOSTNAME_PATTERN = Pattern.compile("[a-zA-Z-]");
+	
 	public static void pingUrl(String Url) {
 		try {
 			URL url = new URL(Url);
@@ -58,4 +72,96 @@ public static void openInBrowser(String url) {
 			e.printStackTrace();
 		}
 	}
+	
+	/**
+	 * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
+	 * port. <code>hostname</code> may represent a valid DNS hostname or an IP address. If
+	 * <code>hostname</code> is a valid DNS hostname <em>and</em> <code>port</code> is equal
+	 * to {@link ServerItem#DEFAULT_PORT} (implying the user may not have specified a server
+	 * port), a <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a> lookup may
+	 * be attempted&mdash;see {@link #resolve(String)} for implementation details.
+	 * <p>
+	 * This method is the equivalent of passing <code>true</code> to {@link #resolve(String, int, boolean)}.
+	 * 
+	 * @param hostname the DNS hostname to resolve.
+	 * @param port the port number to encapsulate within the <code>InetSocketAddress</code>.
+	 * @return an {@link InetSocketAddress}, which may be marked unresolved if hostname lookup failed.
+	 */
+	public static InetSocketAddress resolve(String hostname, int port) {
+		return resolve(hostname, port, true);
+	}
+	
+	/**
+	 * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
+	 * port. An optional <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a>
+	 * lookup may be attempted&mdash;see {@link #resolve(String)} for implementation details.
+	 * A SRV record lookup will only be attempted if <code>hostname</code> represents a valid
+	 * DNS hostname, and <code>port</code> is equal to {@link ServerItem#DEFAULT_PORT} (implying
+	 * the user may not have specified a server port).
+	 * <p>
+	 * If <code>srv</code> is <code>true</code> and SRV record lookup fails or returns no
+	 * results, a regular DNS lookup will be attempted.
+	 * <p>
+	 * If the given <code>hostname</code> represents an IP address, it will not be resolved.
+	 * 
+	 * @param hostname the DNS hostname to resolve.
+	 * @param port the port number to encapsulate within the <code>InetSocketAddress</code>.
+	 * @param srv whether to attempt a SRV record lookup.
+	 * @return an {@link InetSocketAddress}, which may be marked unresolved if hostname lookup failed.
+	 */
+	public static InetSocketAddress resolve(String hostname, int port, boolean srv) {
+		if (srv && (port == ServerItem.DEFAULT_PORT) && (HOSTNAME_PATTERN.matcher(hostname).find())) {
+			try {
+				InetSocketAddress address = resolve(hostname);
+				if (address != null) {
+					return address;
+				}
+			} catch (TextParseException e) {
+				// Do nothing: fall back on a regular DNS lookup before failing
+			}
+		}
+		
+		return new InetSocketAddress(hostname, port);
+	}
+	
+	/**
+	 * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
+	 * port, using a <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a> lookup.
+	 * This method assumes <code>minecraft</code> as the service name during the DNS query,
+	 * such that a matching record looks like:
+	 * <p>
+	 * <code>_minecraft._tcp.example.com. 86400 IN SRV 0 1 25565 minecraft.example.com.</code>
+	 * <p>
+	 * If multiple SRV records exist for a given hostname, the record with the highest priority
+	 * (that is, the lowest priority value) is selected. This implementation does not take
+	 * into account relative weights for records with identical priorities, and behavior in
+	 * such cases is undefined.
+	 * 
+	 * @param hostname the DNS hostname to on which to perform a SRV lookup.
+	 * @return an {@link InetSocketAddress}, or <code>null</code> if no SRV record was found.
+	 * @throws TextParseException if the hostname is malformed.
+	 */
+	public static InetSocketAddress resolve(String hostname) throws TextParseException {
+		String query = "_minecraft._tcp." + hostname.trim();
+		Record[] records = new Lookup(query, Type.SRV).run();
+		
+		if ((records != null) && (records.length > 0)) {
+			SRVRecord srv = (SRVRecord)records[0];
+			
+			if (records.length > 1) {
+				for (int i = 1; i < records.length; i++) {
+					SRVRecord record = (SRVRecord)records[i];
+					if (record.getPriority() < srv.getPriority()) {
+						srv = record;
+					}
+				}
+			}
+			
+			String host = srv.getTarget().toString().replaceAll("\\.+$", "");
+			int port = srv.getPort();
+			return new InetSocketAddress(host, port);
+		}
+		
+		return null;
+	}
 }