JoinGamePacket

protocol/src/main/java/mc/protocol/Difficulty.java

@@ -0,0 +1,15 @@
+package mc.protocol;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+@Getter
+public enum Difficulty {
+	PEACEFUL(0),
+	EASY(1),
+	NORMAL(2),
+	HARD(3);
+
+	private final int id;
+}

protocol/src/main/java/mc/protocol/GameMode.java

@@ -0,0 +1,15 @@
+package mc.protocol;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+@Getter
+public enum GameMode {
+	SURVIVAL(0),
+	CREATIVE(1),
+	ADVENTURE(2),
+	SPECTATOR(3);
+
+	private final int id;
+}

protocol/src/main/java/mc/protocol/LevelType.java

@@ -0,0 +1,16 @@
+package mc.protocol;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+@Getter
+public enum LevelType {
+	DEFAULT_TYPE("default"),
+	FLAT("flat"),
+	LARGE_BIOMES("largeBiomes"),
+	AMPLIFIED("amplified"),
+	DEFAULT_1_1("default_1_1");
+
+	private final String type;
+}

protocol/src/main/java/mc/protocol/State.java

@@ -10,6 +10,7 @@ import mc.protocol.packets.client.HandshakePacket;
 import mc.protocol.packets.client.LoginStartPacket;
 import mc.protocol.packets.client.StatusServerRequestPacket;
 import mc.protocol.packets.server.DisconnectPacket;
+import mc.protocol.packets.server.JoinGamePacket;
 import mc.protocol.packets.server.LoginSuccessPacket;
 import mc.protocol.packets.server.StatusServerResponse;
 
@@ -44,6 +45,12 @@ public enum State {
 					DisconnectPacket.class, 0x00,
 					LoginSuccessPacket.class, 0x02
 			)
+	),
+	PLAY(3,
+			// server bound
+			Map.of(),
+			// client bound
+			Map.of(JoinGamePacket.class, 0x23)
 	);
 
 	@Nullable

protocol/src/main/java/mc/protocol/io/NetByteBuf.java

@@ -49,6 +49,10 @@ public class NetByteBuf extends ByteBuf {
 	@Delegate
 	private final ByteBuf byteBuf;
 
+	public void writeUnsignedByte(int value) {
+		byteBuf.writeByte((byte)(value & 0xFF));
+	}
+
 	//region String
 	public String readString() {
 		return readString(Short.MAX_VALUE);

protocol/src/main/java/mc/protocol/packets/server/JoinGamePacket.java

@@ -0,0 +1,59 @@
+package mc.protocol.packets.server;
+
+import lombok.Data;
+import mc.protocol.Difficulty;
+import mc.protocol.GameMode;
+import mc.protocol.LevelType;
+import mc.protocol.io.NetByteBuf;
+import mc.protocol.packets.ServerSidePacket;
+
+/**
+ * Join game packet.
+ *
+ * <p>Структура пакета</p>
+ * <pre>
+ * | FIELD              | TYPE          | NOTES                                                                |
+ * |--------------------|---------------|----------------------------------------------------------------------|
+ * | Entity ID          | Integer       | ID сущности (игрока)                                                 |
+ * | Gamemode           | Unsigned Byte | 0: Survival                                                          |
+ * |                    |               | 1: Creative                                                          |
+ * |                    |               | 2: Adventure                                                         |
+ * |                    |               | 3: Spectator                                                         |
+ * |                    |               | Bit 3 (0x8) is the hardcore flag.                                    |
+ * | Dimension          | Integer       | -1: Nether                                                           |
+ * |                    |               | 0: Overworld                                                         |
+ * |                    |               | 1: End                                                               |
+ * | Difficulty         | Unsigned Byte | 0: peaceful                                                          |
+ * |                    |               | 1: easy                                                              |
+ * |                    |               | 2: normal                                                            |
+ * |                    |               | 3: hard                                                              |
+ * | Max Players        | Unsigned Byte | Когда-то использовался клиентом для                                  |
+ * |                    |               | отображения списка игроков. Теперь не используется                   |
+ * | Level Type         | String (16)   | Принимает одно из значений:                                          |
+ * |                    |               | default, flat, largeBiomes, amplified, default_1_1                   |
+ * | Reduced Debug Info | Boolean       | Если true, то Клиент отображает меньше отладочной информации (в F3?) |
+ * </pre>
+ *
+ * @see <a href="https://wiki.vg/index.php?title=Protocol&oldid=14204#Join_Game">Join Game</a>
+ */
+@Data
+public class JoinGamePacket implements ServerSidePacket {
+
+	private int entityId;
+	private GameMode gameMode;
+	private int dimension;
+	private Difficulty difficulty;
+	private LevelType levelType;
+	private boolean reducedDebugInfo;
+
+	@Override
+	public void writeSelf(NetByteBuf netByteBuf) {
+		netByteBuf.writeInt(entityId);
+		netByteBuf.writeUnsignedByte(gameMode.getId());
+		netByteBuf.writeInt(dimension);
+		netByteBuf.writeUnsignedByte(difficulty.getId());
+		netByteBuf.writeUnsignedByte(0); // Max Players, unused
+		netByteBuf.writeString(levelType.getType());
+		netByteBuf.writeBoolean(reducedDebugInfo);
+	}
+}