Minecraft-Realms-Emulator/Minecraft-Realms-Emulator/Shared/Helpers/MinecraftServerQuery.cs

using Minecraft_Realms_Emulator.Shared.Responses;
using Newtonsoft.Json;
using System.Net.Sockets;
using System.Text;

namespace Minecraft_Realms_Emulator.Shared.Helpers
{
    public class MinecraftServerQuery
    {
        public MinecraftServerQueryRepsonse? Query(string address)
        {
            string server = address.Split(':')[0];
            int port = address.Contains(':') ? int.Parse(address.Split(':')[1]) : 25565;

            try
            {
                using (TcpClient client = new())
                {
                    client.Connect(server, port);

                    using (NetworkStream stream = client.GetStream())
                    using (BinaryWriter writer = new(stream))
                    using (BinaryReader reader = new(stream))
                    {
                        // Send Handshake packet (https://wiki.vg/Protocol#Handshake)
                        byte[] handshakePacket = CreateHandshakePacket(server, port);
                        writer.Write((byte)handshakePacket.Length); // Packet length
                        writer.Write(handshakePacket); // Packet data

                        // Send Status Request packet (https://wiki.vg/Protocol#Request)
                        writer.Write((byte)0x01); // Packet length
                        writer.Write((byte)0x00); // Packet ID (Request)

                        // Read the response length
                        int length = ReadVarInt(reader);
                        // Read the response packet ID
                        int packetId = ReadVarInt(reader);
                        if (packetId != 0x00) throw new Exception("Invalid packet ID");

                        // Read the JSON length
                        int jsonLength = ReadVarInt(reader);
                        // Read the JSON response
                        byte[] jsonData = reader.ReadBytes(jsonLength);
                        string json = Encoding.UTF8.GetString(jsonData);

                        return JsonConvert.DeserializeObject<MinecraftServerQueryRepsonse>(json);
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: " + ex.Message);
                return null;
            }
        }

        private static byte[] CreateHandshakePacket(string server, int port)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                using (BinaryWriter writer = new BinaryWriter(ms))
                {
                    WriteVarInt(writer, 0x00); // Packet ID (Handshake)
                    WriteVarInt(writer, 754); // Protocol version (754 for Minecraft 1.16.5)
                    WriteVarInt(writer, server.Length); // Server address length
                    writer.Write(Encoding.UTF8.GetBytes(server)); // Server address
                    writer.Write((ushort)port); // Server port
                    WriteVarInt(writer, 1); // Next state (1 for status)

                    return ms.ToArray();
                }
            }
        }

        private static int ReadVarInt(BinaryReader reader)
        {
            int value = 0;
            int size = 0;
            int b;
            while (((b = reader.ReadByte()) & 0x80) == 0x80)
            {
                value |= (b & 0x7F) << (size++ * 7);
                if (size > 5) throw new Exception("VarInt is too big");
            }
            return value | (b << (size * 7));
        }

        private static void WriteVarInt(BinaryWriter writer, int value)
        {
            while ((value & 0xFFFFFF80) != 0)
            {
                writer.Write((byte)((value & 0x7F) | 0x80));
                value >>= 7;
            }
            writer.Write((byte)(value & 0x7F));
        }
    }
}