Your code. Their Minecraft client.

import { Server } from "mc-protocol";

const server = new Server({
  port: 25565,
  autoInit: true,
  autoKeepAlive: true,
  compressionThreshold: 256,
});

server.on("Status/StatusRequest", (client) => {
  client.sendPacket("StatusResponse", {
    jsonResponse: {
      version: { name: "26.2", protocol: 776 },
      players: { max: 20, online: server.clients.size },
      description: { text: "My server" },
    },
  }).catch(console.error);
});

server.on("Status/PingRequest", (client, data) => {
  client.sendPacket("PongResponse", {
    timestamp: data.timestamp,
  }).catch(console.error);
});

server.on("playerJoin", (client, session) => {
  console.log(`${session.username} joined`);
});

import { Client } from "mc-protocol";

const client = new Client({ host: "localhost", port: 25565 });

client.on("Socket:Ready", async () => {
  await client.sendPacket("Intension", {
    protocolVersion: 776,
    serverHost: "localhost",
    serverPort: 25565,
    nextState: 2,
  });
  await client.sendPacket("Hello", {
    username: "bot",
    playerUUID: "00000000000000000000000000000000",
  });
});

client.on("Login/LoginFinished", () => {
  client.sendPacket("LoginAcknowledged");
});
client.on("Config/SelectKnownPacks", ({ knownPacks }) => {
  client.sendPacket("SelectKnownPacks", { knownPacks });
});
client.on("Config/FinishConfiguration", () => {
  client.sendPacket("FinishConfiguration");
});
client.on("playerJoin", (s) => console.log(`in as ${s.username}`));

import { Proxy } from "mc-protocol";

const proxy = new Proxy({
  listen: { host: "0.0.0.0", port: 25566 },
  upstream: { host: "play.example.net", port: 25565 },
});

proxy.Client.on("ChatCommand", async (player, data, next) => {
  console.log(`${player.session.username} ran /${data.command}`);
  await next(data);
});

proxy.Server.on("SetPlayerInventory", (_server, data, next) => {
  if (shouldHideInventory(data)) return next(null);
  return next(data);
});