McProtoNet

using McProtoNet;
using McProtoNet.Protocol;
using HandshakeSb = McProtoNet.Protocol.Packets.Handshaking.Serverbound;
using LoginSb = McProtoNet.Protocol.Packets.Login.Serverbound;

const int Pv = 772;                                    // 1.21.8

await using var client = new MinecraftClient(
    new MinecraftClientOptions { Host = "127.0.0.1", Port = 25565 });
await client.ConnectAsync();

await client.SendAsync(
    new HandshakeSb.SetProtocolPacket(Pv, "127.0.0.1", 25565, 2), Pv);
await client.SendAsync(
    new LoginSb.LoginStartPacket("McProtoBot", V764_Last: new(Guid.NewGuid())),
    Pv);

var bot = new Bot(client, Pv);                         // the class from First bot

await foreach (var packet in client.ReadPacketsAsync())
    await bot.HandleAsync(in packet, Pv);