Decided to use one version. Compatibility with other can be achieved woth protocol hack on proxy side

src/main/java/ru/nanit/limbo/connection/ClientConnection.java

@@ -7,7 +7,6 @@ import io.netty.channel.ChannelInboundHandlerAdapter;
 import ru.nanit.limbo.LimboConfig;
 import ru.nanit.limbo.protocol.packets.login.*;
 import ru.nanit.limbo.protocol.packets.play.*;
-import ru.nanit.limbo.protocol.registry.Version;
 import ru.nanit.limbo.protocol.pipeline.PacketDecoder;
 import ru.nanit.limbo.protocol.pipeline.PacketEncoder;
 import ru.nanit.limbo.protocol.packets.PacketHandshake;
@@ -15,6 +14,7 @@ import ru.nanit.limbo.protocol.packets.status.PacketStatusPing;
 import ru.nanit.limbo.protocol.packets.status.PacketStatusRequest;
 import ru.nanit.limbo.protocol.packets.status.PacketStatusResponse;
 import ru.nanit.limbo.protocol.registry.State;
+import ru.nanit.limbo.protocol.registry.Version;
 import ru.nanit.limbo.server.LimboServer;
 import ru.nanit.limbo.util.Logger;
 import ru.nanit.limbo.util.UuidUtil;
@@ -29,6 +29,7 @@ public class ClientConnection extends ChannelInboundHandlerAdapter {
     private final Channel channel;
 
     private State state;
+    private Version clientVersion;
 
     private UUID uuid;
     private String username;
@@ -66,12 +67,12 @@ public class ClientConnection extends ChannelInboundHandlerAdapter {
     public void handlePacket(Object packet){
         if (packet instanceof PacketHandshake){
             PacketHandshake handshake = (PacketHandshake) packet;
-            State state = State.getById(handshake.getNextState());
+            updateState(State.getById(handshake.getNextState()));
-            updateStateAndVersion(state, handshake.getVersion());
+            clientVersion = handshake.getVersion();
         }
 
         if (packet instanceof PacketStatusRequest){
-            sendPacket(new PacketStatusResponse());
+            sendPacket(new PacketStatusResponse(server.getConnectionsCount()));
         }
 
         if (packet instanceof PacketStatusPing){
@@ -84,6 +85,11 @@ public class ClientConnection extends ChannelInboundHandlerAdapter {
                 return;
             }
 
+            if (!clientVersion.equals(Version.getCurrentSupported())){
+                disconnect("Incompatible client version");
+                return;
+            }
+
             this.username = ((PacketLoginStart) packet).getUsername();
             this.uuid = UuidUtil.getOfflineModeUuid(this.username);
 
@@ -96,7 +102,7 @@ public class ClientConnection extends ChannelInboundHandlerAdapter {
             updateState(State.PLAY);
 
             server.addConnection(this);
-            Logger.info("Player %s connected", this.username);
+            Logger.info("Player %s connected (%s)", this.username, channel.remoteAddress());
 
             sendJoinPackets();
         }
@@ -179,16 +185,4 @@ public class ClientConnection extends ChannelInboundHandlerAdapter {
         channel.pipeline().get(PacketDecoder.class).updateState(state);
         channel.pipeline().get(PacketEncoder.class).updateState(state);
     }
-
-    public void updateStateAndVersion(State state, Version version){
-        PacketDecoder decoder = channel.pipeline().get(PacketDecoder.class);
-        PacketEncoder encoder = channel.pipeline().get(PacketEncoder.class);
-
-        decoder.updateVersion(version);
-        decoder.updateState(state);
-        encoder.updateVersion(version);
-        encoder.updateState(state);
-
-        this.state = state;
-    }
 }

src/main/java/ru/nanit/limbo/protocol/Packet.java

@@ -1,11 +1,9 @@
 package ru.nanit.limbo.protocol;
 
-import ru.nanit.limbo.protocol.registry.Version;
-
 public interface Packet {
 
-    void encode(ByteMessage msg, Version version);
+    void encode(ByteMessage msg);
 
-    void decode(ByteMessage msg, Version version);
+    void decode(ByteMessage msg);
 
 }

src/main/java/ru/nanit/limbo/protocol/PacketIn.java

@@ -1,11 +1,9 @@
 package ru.nanit.limbo.protocol;
 
-import ru.nanit.limbo.protocol.registry.Version;
-
 public interface PacketIn extends Packet {
 
     @Override
-    default void encode(ByteMessage msg, Version version) {
+    default void encode(ByteMessage msg) {
         // Can be ignored for incoming packets
     }
 

src/main/java/ru/nanit/limbo/protocol/PacketOut.java

@@ -1,11 +1,9 @@
 package ru.nanit.limbo.protocol;
 
-import ru.nanit.limbo.protocol.registry.Version;
-
 public interface PacketOut extends Packet {
 
     @Override
-    default void decode(ByteMessage msg, Version version) {
+    default void decode(ByteMessage msg) {
         // Can be ignored for outgoing packets
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/PacketHandshake.java

@@ -44,7 +44,7 @@ public class PacketHandshake implements Packet {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeVarInt(this.version.getProtocolNumber());
         msg.writeString(host);
         msg.writeShort(port);
@@ -52,7 +52,7 @@ public class PacketHandshake implements Packet {
     }
 
     @Override
-    public void decode(ByteMessage msg, Version version) {
+    public void decode(ByteMessage msg) {
         this.version = Version.of(msg.readVarInt());
         this.host = msg.readString();
         this.port = msg.readUnsignedShort();

src/main/java/ru/nanit/limbo/protocol/packets/login/PacketDisconnect.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.login;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketDisconnect implements PacketOut {
 
@@ -13,7 +12,7 @@ public class PacketDisconnect implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeString(String.format("{\"text\": \"%s\"}", reason));
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/login/PacketLoginStart.java

@@ -1,7 +1,6 @@
 package ru.nanit.limbo.protocol.packets.login;
 
 import ru.nanit.limbo.protocol.*;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketLoginStart implements PacketIn {
 
@@ -12,7 +11,7 @@ public class PacketLoginStart implements PacketIn {
     }
 
     @Override
-    public void decode(ByteMessage msg, Version version) {
+    public void decode(ByteMessage msg) {
         this.username = msg.readString();
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/login/PacketLoginSuccess.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.login;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 import java.util.UUID;
 
@@ -20,7 +19,7 @@ public class PacketLoginSuccess implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeUuid(uuid);
         msg.writeString(username);
     }

src/main/java/ru/nanit/limbo/protocol/packets/play/PacketBossBar.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.play;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 import java.util.UUID;
 
@@ -40,7 +39,7 @@ public class PacketBossBar implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeUuid(uuid);
         msg.writeVarInt(0); // Create bossbar
         msg.writeString(title);

src/main/java/ru/nanit/limbo/protocol/packets/play/PacketChatMessage.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.play;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 import java.util.UUID;
 
@@ -25,7 +24,7 @@ public class PacketChatMessage implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeString(jsonData);
         msg.writeByte(position.index);
         msg.writeUuid(sender);

src/main/java/ru/nanit/limbo/protocol/packets/play/PacketJoinGame.java

@@ -3,7 +3,6 @@ package ru.nanit.limbo.protocol.packets.play;
 import net.kyori.adventure.nbt.CompoundBinaryTag;
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketJoinGame implements PacketOut {
 
@@ -84,7 +83,7 @@ public class PacketJoinGame implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeInt(entityId);
         msg.writeBoolean(isHardcore);
         msg.writeByte(gameMode);

src/main/java/ru/nanit/limbo/protocol/packets/play/PacketKeepAlive.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.play;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.Packet;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketKeepAlive implements Packet {
 
@@ -17,12 +16,12 @@ public class PacketKeepAlive implements Packet {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeLong(id);
     }
 
     @Override
-    public void decode(ByteMessage msg, Version version) {
+    public void decode(ByteMessage msg) {
         this.id = msg.readLong();
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/play/PacketPlayerPositionAndLook.java

@@ -2,7 +2,6 @@ package ru.nanit.limbo.protocol.packets.play;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.PacketOut;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketPlayerPositionAndLook implements PacketOut {
 
@@ -43,7 +42,7 @@ public class PacketPlayerPositionAndLook implements PacketOut {
     }
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeDouble(x);
         msg.writeDouble(y);
         msg.writeDouble(z);

src/main/java/ru/nanit/limbo/protocol/packets/status/PacketStatusPing.java

@@ -2,19 +2,18 @@ package ru.nanit.limbo.protocol.packets.status;
 
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.Packet;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketStatusPing implements Packet {
 
     private long randomId;
 
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         msg.writeLong(randomId);
     }
 
     @Override
-    public void decode(ByteMessage msg, Version version) {
+    public void decode(ByteMessage msg) {
         this.randomId = msg.readLong();
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/status/PacketStatusRequest.java

@@ -1,12 +1,11 @@
 package ru.nanit.limbo.protocol.packets.status;
 
 import ru.nanit.limbo.protocol.*;
-import ru.nanit.limbo.protocol.registry.Version;
 
 public class PacketStatusRequest implements PacketIn {
 
     @Override
-    public void decode(ByteMessage msg, Version version) {
+    public void decode(ByteMessage msg) {
 
     }
 

src/main/java/ru/nanit/limbo/protocol/packets/status/PacketStatusResponse.java

@@ -8,11 +8,20 @@ public class PacketStatusResponse implements PacketOut {
 
     private static final String TEMPLATE = "{ \"version\": { \"name\": \"%s\", \"protocol\": %d }, \"players\": { \"max\": %d, \"online\": %d, \"sample\": [] }, \"description\": %s }";
 
+    private int online;
+
+    public PacketStatusResponse(){ }
+
+    public PacketStatusResponse(int online){
+        this.online = online;
+    }
+
     @Override
-    public void encode(ByteMessage msg, Version version) {
+    public void encode(ByteMessage msg) {
         String ver = LimboConfig.getPingData().getVersion();
         String desc = LimboConfig.getPingData().getDescription();
-        String json = getResponseJson(ver, version.getProtocolNumber(), LimboConfig.getMaxPlayers(), 0, desc);
+        String json = getResponseJson(ver, Version.getCurrentSupported().getProtocolNumber(),
+                LimboConfig.getMaxPlayers(), online, desc);
         msg.writeString(json);
     }
 

src/main/java/ru/nanit/limbo/protocol/pipeline/PacketDecoder.java

@@ -5,18 +5,15 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToMessageDecoder;
 import ru.nanit.limbo.protocol.*;
 import ru.nanit.limbo.protocol.registry.State;
-import ru.nanit.limbo.protocol.registry.Version;
 import ru.nanit.limbo.util.Logger;
 
 import java.util.List;
 
 public class PacketDecoder extends MessageToMessageDecoder<ByteBuf> {
 
-    private State.PacketVersionRegistry.PacketIdRegistry<?> mappings;
+    private State.PacketRegistry mappings;
-    private Version version;
 
     public PacketDecoder(){
-        updateVersion(Version.getMinimal());
         updateState(State.HANDSHAKING);
     }
 
@@ -30,7 +27,7 @@ public class PacketDecoder extends MessageToMessageDecoder<ByteBuf> {
 
         if (packet != null){
             try {
-                packet.decode(msg, mappings.getVersion());
+                packet.decode(msg);
             } catch (Exception e){
                 Logger.warning("Cannot decode packet 0x%s: %s", Integer.toHexString(packetId), e.getMessage());
             }
@@ -41,12 +38,8 @@ public class PacketDecoder extends MessageToMessageDecoder<ByteBuf> {
         }
     }
 
-    public void updateVersion(Version version){
-        this.version = version;
-    }
-
     public void updateState(State state){
-        this.mappings = state.serverBound.getRegistry(version);
+        this.mappings = state.serverBound;
     }
 
 }

src/main/java/ru/nanit/limbo/protocol/pipeline/PacketEncoder.java

@@ -5,26 +5,23 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToByteEncoder;
 import ru.nanit.limbo.protocol.ByteMessage;
 import ru.nanit.limbo.protocol.Packet;
-import ru.nanit.limbo.protocol.registry.Version;
 import ru.nanit.limbo.protocol.registry.State;
 import ru.nanit.limbo.util.Logger;
 
 public class PacketEncoder extends MessageToByteEncoder<Packet> {
 
-    private State.PacketVersionRegistry.PacketIdRegistry<?> mappings;
+    private State.PacketRegistry registry;
-    private Version version;
 
     public PacketEncoder(){
-        updateVersion(Version.getMinimal());
         updateState(State.HANDSHAKING);
     }
 
     @Override
     protected void encode(ChannelHandlerContext ctx, Packet packet, ByteBuf out) throws Exception {
-        if (mappings == null) return;
+        if (registry == null) return;
 
         ByteMessage msg = new ByteMessage(out);
-        int packetId = mappings.getPacketId(packet.getClass());
+        int packetId = registry.getPacketId(packet.getClass());
 
         if (packetId == -1){
             Logger.warning("Undefined packet class: %s", packet.getClass().getName());
@@ -34,18 +31,14 @@ public class PacketEncoder extends MessageToByteEncoder<Packet> {
         msg.writeVarInt(packetId);
 
         try {
-            packet.encode(msg, version);
+            packet.encode(msg);
         } catch (Exception e){
             Logger.warning("Cannot encode packet 0x%s: %s", Integer.toHexString(packetId), e.getMessage());
         }
     }
 
-    public void updateVersion(Version version){
-        this.version = version;
-    }
-
     public void updateState(State state){
-        this.mappings = state.clientBound.getRegistry(version);
+        this.registry = state.clientBound;
     }
 
 }

src/main/java/ru/nanit/limbo/protocol/registry/State.java

@@ -16,39 +16,35 @@ public enum State {
 
     HANDSHAKING(0){
         {
-            serverBound.register(Version.getMinimal(), 0x00, PacketHandshake::new);
+            serverBound.register(0x00, PacketHandshake::new);
         }
     },
     STATUS(1){
         {
-            serverBound.register(Version.getMinimal(), 0x01, PacketStatusPing::new);
+            serverBound.register(0x01, PacketStatusPing::new);
-            serverBound.register(Version.getMinimal(), 0x00, PacketStatusRequest::new);
+            serverBound.register(0x00, PacketStatusRequest::new);
-            clientBound.register(Version.getMinimal(), 0x00, PacketStatusResponse::new);
+            clientBound.register(0x00, PacketStatusResponse::new);
-            clientBound.register(Version.getMinimal(), 0x01, PacketStatusPing::new);
+            clientBound.register(0x01, PacketStatusPing::new);
         }
     },
     LOGIN(2){
         {
-            serverBound.register(Version.getMinimal(), 0x00, PacketLoginStart::new);
+            serverBound.register(0x00, PacketLoginStart::new);
-            clientBound.register(Version.getMinimal(), 0x00, PacketDisconnect::new);
+            clientBound.register(0x00, PacketDisconnect::new);
-            clientBound.register(Version.getMinimal(), 0x02, PacketLoginSuccess::new);
+            clientBound.register(0x02, PacketLoginSuccess::new);
         }
     },
     PLAY(3){
         {
-            serverBound.register(Version.V1_16_4, 0x10, PacketKeepAlive::new);
+            serverBound.register(0x10, PacketKeepAlive::new);
-            clientBound.register(Version.V1_16_4, 0x24, PacketJoinGame::new);
+            clientBound.register(0x24, PacketJoinGame::new);
-            clientBound.register(Version.V1_16_4, 0x34, PacketPlayerPositionAndLook::new);
+            clientBound.register(0x34, PacketPlayerPositionAndLook::new);
-            clientBound.register(Version.V1_16_4, 0x1F, PacketKeepAlive::new);
+            clientBound.register(0x1F, PacketKeepAlive::new);
-            clientBound.register(Version.V1_16_4, 0x0E, PacketChatMessage::new);
+            clientBound.register(0x0E, PacketChatMessage::new);
-            clientBound.register(Version.V1_16_4, 0x0C, PacketBossBar::new);
+            clientBound.register(0x0C, PacketBossBar::new);
         }
     };
 
-    private final int stateId;
-    public final PacketVersionRegistry serverBound = new PacketVersionRegistry();
-    public final PacketVersionRegistry clientBound = new PacketVersionRegistry();
-
     private static final Map<Integer, State> STATE_BY_ID = new HashMap<>();
 
     static {
@@ -57,6 +53,10 @@ public enum State {
         }
     }
 
+    private final int stateId;
+    public final PacketRegistry serverBound = new PacketRegistry();
+    public final PacketRegistry clientBound = new PacketRegistry();
+
     State(int stateId){
         this.stateId = stateId;
     }
@@ -65,6 +65,31 @@ public enum State {
         return STATE_BY_ID.get(stateId);
     }
 
+    public static class PacketRegistry {
+
+        private final Map<Integer, Supplier<?>> packetsById = new HashMap<>();
+        private final Map<Class<?>, Integer> packetIdByClass = new HashMap<>();
+
+        public Packet getPacket(int packetId){
+            Supplier<?> supplier = packetsById.get(packetId);
+            return supplier == null ? null : (Packet) supplier.get();
+        }
+
+        public int getPacketId(Class<?> packetClass){
+            return packetIdByClass.getOrDefault(packetClass, -1);
+        }
+
+        public void register(int packetId, Supplier<?> supplier){
+            packetsById.put(packetId, supplier);
+            packetIdByClass.put(supplier.get().getClass(), packetId);
+        }
+
+    }
+
+    /*
+
+    Temporary don't needed
+
     public static class PacketVersionRegistry {
 
         private final Map<Version, PacketIdRegistry<?>> MAPPINGS = new HashMap<>();
@@ -109,6 +134,6 @@ public enum State {
 
         }
 
-    }
+    }*/
 
 }

src/main/java/ru/nanit/limbo/protocol/registry/Version.java

@@ -1,6 +1,5 @@
 package ru.nanit.limbo.protocol.registry;
 
-import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -44,8 +43,8 @@ public enum Version {
         }
     }
 
-    public static Version getMinimal(){
+    public static Version getCurrentSupported(){
-        return V1_9;
+        return V1_16_4;
     }
 
     public static Version of(int protocolNumber){
@@ -62,16 +61,4 @@ public enum Version {
         return this.protocolNumber;
     }
 
-    public Version getClosest(Collection<Version> available){
-        Version closest = getMinimal();
-
-        for (Version version : available){
-            if (version.protocolNumber > closest.protocolNumber && version.protocolNumber < this.protocolNumber){
-                closest = version;
-            }
-        }
-
-        return closest;
-    }
-
 }

src/main/resources/settings.properties

@@ -18,6 +18,8 @@ ping-version=NanoLimbo
 ping-description={"text": "NanoLimbo"}
 
 # Player info forwarding support. Available types: NONE, LEGACY, MODERN
+# MODERN - Velocity native forwarding type.
+# LEGACY - BungeeCord forwarding type (Velocity supports it too)
 ip-forwarding=LEGACY
 
 # If you use MODERN type of forwarding, enter your secret code here