Made the server not accept Packet27 as it is not used.

src/main/java/net/minecraft/server/Packet.java

@@ -0,0 +1,205 @@
+package net.minecraft.server;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.EOFException;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public abstract class Packet {
+
+    private static Map a = new HashMap();
+    private static Map b = new HashMap();
+    private static Set c = new HashSet();
+    private static Set d = new HashSet();
+    public final long timestamp = System.currentTimeMillis();
+    public boolean k = false;
+    private static HashMap e;
+    private static int f;
+
+    public Packet() {}
+
+    static void a(int i, boolean flag, boolean flag1, Class oclass) {
+        if (a.containsKey(Integer.valueOf(i))) {
+            throw new IllegalArgumentException("Duplicate packet id:" + i);
+        } else if (b.containsKey(oclass)) {
+            throw new IllegalArgumentException("Duplicate packet class:" + oclass);
+        } else {
+            a.put(Integer.valueOf(i), oclass);
+            b.put(oclass, Integer.valueOf(i));
+            if (flag) {
+                c.add(Integer.valueOf(i));
+            }
+
+            if (flag1) {
+                d.add(Integer.valueOf(i));
+            }
+        }
+    }
+
+    public static Packet a(int i) {
+        try {
+            Class oclass = (Class) a.get(Integer.valueOf(i));
+
+            return oclass == null ? null : (Packet) oclass.newInstance();
+        } catch (Exception exception) {
+            exception.printStackTrace();
+            System.out.println("Skipping packet with id " + i);
+            return null;
+        }
+    }
+
+    public final int b() {
+        return ((Integer) b.get(this.getClass())).intValue();
+    }
+
+    // CraftBukkit - throws IOException
+    public static Packet a(DataInputStream datainputstream, boolean flag) throws IOException {
+        boolean flag1 = false;
+        Packet packet = null;
+
+        int i;
+
+        try {
+            i = datainputstream.read();
+            if (i == -1) {
+                return null;
+            }
+
+            if (flag && !d.contains(Integer.valueOf(i)) || !flag && !c.contains(Integer.valueOf(i))) {
+                throw new IOException("Bad packet id " + i);
+            }
+
+            packet = a(i);
+            if (packet == null) {
+                throw new IOException("Bad packet id " + i);
+            }
+
+            packet.a(datainputstream);
+        } catch (EOFException eofexception) {
+            System.out.println("Reached end of stream");
+            return null;
+        }
+
+        PacketCounter packetcounter = (PacketCounter) e.get(Integer.valueOf(i));
+
+        if (packetcounter == null) {
+            packetcounter = new PacketCounter((EmptyClass1) null);
+            e.put(Integer.valueOf(i), packetcounter);
+        }
+
+        packetcounter.a(packet.a());
+        ++f;
+        if (f % 1000 == 0) {
+            ;
+        }
+
+        return packet;
+    }
+
+    // CraftBukkit -  throws IOException
+    public static void a(Packet packet, DataOutputStream dataoutputstream) throws IOException {
+        dataoutputstream.write(packet.b());
+        packet.a(dataoutputstream);
+    }
+
+    // CraftBukkit -  throws IOException
+    public static void a(String s, DataOutputStream dataoutputstream)  throws IOException {
+        if (s.length() > 32767) {
+            throw new IOException("String too big");
+        } else {
+            dataoutputstream.writeShort(s.length());
+            dataoutputstream.writeChars(s);
+        }
+    }
+
+    // CraftBukkit -  throws IOException
+    public static String a(DataInputStream datainputstream, int i)  throws IOException {
+        short short1 = datainputstream.readShort();
+
+        if (short1 > i) {
+            throw new IOException("Received string length longer than maximum allowed (" + short1 + " > " + i + ")");
+        } else if (short1 < 0) {
+            throw new IOException("Received string length is less than zero! Weird string!");
+        } else {
+            StringBuilder stringbuilder = new StringBuilder();
+
+            for (int j = 0; j < short1; ++j) {
+                stringbuilder.append(datainputstream.readChar());
+            }
+
+            return stringbuilder.toString();
+        }
+    }
+
+    public abstract void a(DataInputStream datainputstream);
+
+    public abstract void a(DataOutputStream dataoutputstream);
+
+    public abstract void a(NetHandler nethandler);
+
+    public abstract int a();
+
+    static {
+        a(0, true, true, Packet0KeepAlive.class);
+        a(1, true, true, Packet1Login.class);
+        a(2, true, true, Packet2Handshake.class);
+        a(3, true, true, Packet3Chat.class);
+        a(4, true, false, Packet4UpdateTime.class);
+        a(5, true, false, Packet5EntityEquipment.class);
+        a(6, true, false, Packet6SpawnPosition.class);
+        a(7, false, true, Packet7UseEntity.class);
+        a(8, true, false, Packet8UpdateHealth.class);
+        a(9, true, true, Packet9Respawn.class);
+        a(10, true, true, Packet10Flying.class);
+        a(11, true, true, Packet11PlayerPosition.class);
+        a(12, true, true, Packet12PlayerLook.class);
+        a(13, true, true, Packet13PlayerLookMove.class);
+        a(14, false, true, Packet14BlockDig.class);
+        a(15, false, true, Packet15Place.class);
+        a(16, false, true, Packet16BlockItemSwitch.class);
+        a(17, true, false, Packet17.class);
+        a(18, true, true, Packet18ArmAnimation.class);
+        a(19, false, true, Packet19EntityAction.class);
+        a(20, true, false, Packet20NamedEntitySpawn.class);
+        a(21, true, false, Packet21PickupSpawn.class);
+        a(22, true, false, Packet22Collect.class);
+        a(23, true, false, Packet23VehicleSpawn.class);
+        a(24, true, false, Packet24MobSpawn.class);
+        a(25, true, false, Packet25EntityPainting.class);
+        a(27, false, false, Packet27.class); // CraftBukkit - true -> false; disabled unused packet.
+        a(28, true, false, Packet28EntityVelocity.class);
+        a(29, true, false, Packet29DestroyEntity.class);
+        a(30, true, false, Packet30Entity.class);
+        a(31, true, false, Packet31RelEntityMove.class);
+        a(32, true, false, Packet32EntityLook.class);
+        a(33, true, false, Packet33RelEntityMoveLook.class);
+        a(34, true, false, Packet34EntityTeleport.class);
+        a(38, true, false, Packet38EntityStatus.class);
+        a(39, true, false, Packet39AttachEntity.class);
+        a(40, true, false, Packet40EntityMetadata.class);
+        a(50, true, false, Packet50PreChunk.class);
+        a(51, true, false, Packet51MapChunk.class);
+        a(52, true, false, Packet52MultiBlockChange.class);
+        a(53, true, false, Packet53BlockChange.class);
+        a(54, true, false, Packet54PlayNoteBlock.class);
+        a(60, true, false, Packet60Explosion.class);
+        a(70, true, false, Packet70Bed.class);
+        a(71, true, false, Packet71Weather.class);
+        a(100, true, false, Packet100OpenWindow.class);
+        a(101, true, true, Packet101CloseWindow.class);
+        a(102, false, true, Packet102WindowClick.class);
+        a(103, true, false, Packet103SetSlot.class);
+        a(104, true, false, Packet104WindowItems.class);
+        a(105, true, false, Packet105CraftProgressBar.class);
+        a(106, true, true, Packet106Transaction.class);
+        a(130, true, true, Packet130UpdateSign.class);
+        a(200, true, false, Packet200Statistic.class);
+        a(255, true, true, Packet255KickDisconnect.class);
+        e = new HashMap();
+        f = 0;
+    }
+}