As per popular request, 1.12 clients for 1.12-pre6 servers.

common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java

@@ -9,6 +9,7 @@ import us.myles.ViaVersion.protocols.protocol1_10to1_9_3.Protocol1_10To1_9_3_4;
 import us.myles.ViaVersion.protocols.protocol1_11_1to1_11.Protocol1_11_1To1_11;
 import us.myles.ViaVersion.protocols.protocol1_11to1_10.Protocol1_11To1_10;
 import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.Protocol1_12To1_11_1;
+import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.Protocol1_12To1_12_Pre6;
 import us.myles.ViaVersion.protocols.protocol1_9_1_2to1_9_3_4.Protocol1_9_1_2TO1_9_3_4;
 import us.myles.ViaVersion.protocols.protocol1_9_1to1_9.Protocol1_9_1TO1_9;
 import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.Protocol1_9_3TO1_9_1_2;
@@ -41,9 +42,10 @@ public class ProtocolRegistry {
 
         registerProtocol(new Protocol1_11To1_10(), Collections.singletonList(ProtocolVersion.v1_11.getId()), ProtocolVersion.v1_10.getId());
         registerProtocol(new Protocol1_11_1To1_11(), Collections.singletonList(ProtocolVersion.v1_11_1.getId()), ProtocolVersion.v1_11.getId());
-
-        // Snapshot
         registerProtocol(new Protocol1_12To1_11_1(), Collections.singletonList(ProtocolVersion.v1_12.getId()), ProtocolVersion.v1_11_1.getId());
+        // 1.12 -> 1.12-pre6 server (as per popular request)
+        registerProtocol(new Protocol1_12To1_12_Pre6(), Collections.singletonList(ProtocolVersion.v1_12.getId()), ProtocolVersion.v1_12_pre6.getId());
+
     }
 
     /**

common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java

@@ -30,6 +30,7 @@ public class ProtocolVersion {
     public static final ProtocolVersion v1_11;
     public static final ProtocolVersion v1_11_1;
     public static final ProtocolVersion v1_12;
+    public static final ProtocolVersion v1_12_pre6;
     public static final ProtocolVersion unknown;
 
     private final int id;
@@ -56,6 +57,7 @@ public class ProtocolVersion {
         register(v1_11 = new ProtocolVersion(315, "1.11"));
         register(v1_11_1 = new ProtocolVersion(316, "1.11.1"));
         register(v1_12 = new ProtocolVersion(335, "1.12"));
+        register(v1_12_pre6 = new ProtocolVersion(333, "1.12-pre6"));
         register(unknown = new ProtocolVersion(-1, "UNKNOWN"));
     }
 

common/src/main/java/us/myles/ViaVersion/protocols/protocol1_12to1_11_1/Protocol1_12To1_12_Pre6.java

@@ -0,0 +1,51 @@
+package us.myles.ViaVersion.protocols.protocol1_12to1_11_1;
+
+import us.myles.ViaVersion.api.PacketWrapper;
+import us.myles.ViaVersion.api.data.UserConnection;
+import us.myles.ViaVersion.api.protocol.Protocol;
+import us.myles.ViaVersion.api.remapper.PacketHandler;
+import us.myles.ViaVersion.api.remapper.PacketRemapper;
+import us.myles.ViaVersion.api.type.Type;
+import us.myles.ViaVersion.packets.State;
+
+public class Protocol1_12To1_12_Pre6 extends Protocol {
+    @Override
+    protected void registerPackets() {
+        registerOutgoing(State.PLAY, 0x48, 0x48, new PacketRemapper() {
+            @Override
+            public void registerMap() {
+                map(Type.VAR_INT); // 0 - Sound name
+                map(Type.VAR_INT); // 1 - Sound Category
+                map(Type.INT); // 2 - x
+                map(Type.INT); // 3 - y
+                map(Type.INT); // 4 - z
+                map(Type.FLOAT); // 5 - Volume
+                map(Type.FLOAT); // 6 - Pitch
+
+                handler(new PacketHandler() {
+                    @Override
+                    public void handle(PacketWrapper wrapper) throws Exception {
+                        int id = wrapper.get(Type.VAR_INT, 0);
+                        id = getNewSoundId(id);
+
+                        if (id == -1) // Removed
+                            wrapper.cancel();
+                        wrapper.set(Type.VAR_INT, 0, id);
+                    }
+                });
+            }
+        });
+    }
+
+    @Override
+    public void init(UserConnection userConnection) {
+
+    }
+
+    private int getNewSoundId(int id) { //TODO Make it better, suggestions are welcome. It's ugly and hardcoded now.
+        int newId = id;
+        if (id >= 544) // UI toast sound
+            newId += 3;
+        return newId;
+    }
+}