Networking

This section covers Hytale’s networking layer and packet handling system.

Overview

The Hytale server uses a sophisticated networking layer based on Netty with support for both QUIC (UDP) and TCP transports. The protocol uses little-endian byte order, Zstd compression for large packets, and variable-length integer encoding.

In This Section

• Protocol & Packets - Wire format, packet structure, and I/O utilities

Quick Reference

Wire Format

[4 bytes] Length (little-endian)
[4 bytes] Packet ID (little-endian)
[...] Payload (may be Zstd-compressed)

Key Characteristics

Feature	Description
Byte Order	Little-endian throughout
Compression	Zstd for large packets
VarInt	7-bit encoding, max 5 bytes
Strings	UTF-8 with VarInt length prefix
Transport	QUIC (UDP) primary, TCP fallback
Max Payload	~1.56GB (0x64000000 bytes)

Packet Interface

public interface Packet {
    int getId();
    void serialize(@Nonnull ByteBuf buffer);
    int computeSize();
}

Intercepting Packets

import com.hypixel.hytale.server.core.io.adapter.PacketAdapters;
import com.hypixel.hytale.server.core.io.adapter.PacketFilter;
import com.hypixel.hytale.server.core.io.adapter.PlayerPacketFilter;

// Player-specific filter (only fires for in-game players)
PacketFilter filter = PacketAdapters.registerInbound(
    (PlayerPacketFilter) (player, packet) -> {
        // Return true to consume/block the packet
        return false;
    }
);

// Cleanup when done
PacketAdapters.deregisterInbound(filter);