Get Minecraft server info by LSP using nodejs.

mineStatus.js

const { Socket } = require('net')

class MineStatus {
  /** @type {Socket} */
  socket

  /** @type {string} */
  host

  /** @type {number} */
  port

  /** @type {number} */
  packageDataLen

  /** @type {Buffer} */
  responseBuffers = Buffer.from('')

  /** @type {{host: string, ip: string, port: string}} */
  debugInfo

  /**
   * @param {string} host
   * @param {number} port
   * @param {boolean} [immediately]
   */
  constructor(host, port) {
    this.host = host
    this.port = port
  }

  onConnect() {
    const hostUnit8Arr = Uint8Array.from(Buffer.from(this.host))
    const dataBody = MineStatus.concatData([
      Uint8Array.from([0x00, 0x00]),
      MineStatus.packVarint(hostUnit8Arr.length),
      hostUnit8Arr,
      MineStatus.concatData([
        Uint8Array.from(Buffer.from(Uint16Array.from([this.port]).buffer)),
        Uint8Array.from([0x01]),
      ]),
    ])

    this.socket.write(MineStatus.concatData([MineStatus.packVarint(dataBody.length), dataBody]))
    this.socket.write(Uint8Array.from([0x01, 0x00]))

    // Set debug info here
    this.debugInfo = {
      host: this.host,
      ip: this.socket.remoteAddress || this.host,
      port: this.socket.remotePort || this.port,
    }
  }

  /** @return {Promise<Buffer>} */
  getResponseData() {
    if (this.responseBuffers.length >= this.packageDataLen) return Promise.resolve(this.responseBuffers)

    this.socket = new Socket().connect({ host: this.host, port: this.port })
    this.socket.on('connect', this.onConnect.bind(this))

    return new Promise((resolve) => {
      this.socket.on('readable', () => {
        if (this.socket.readableLength >= 5) {
          if (this.packageDataLen === undefined) {
            const packageLen = MineStatus.unPackVarint(this.socket)
            const packageId = MineStatus.unPackVarint(this.socket)
            const packageDataLen = MineStatus.unPackVarint(this.socket)

            this.packageDataLen = packageDataLen
          }

          this.responseBuffers = Buffer.concat([this.responseBuffers, this.socket.read()])

          if (this.responseBuffers.length >= this.packageDataLen) {
            this.socket.destroy()
            resolve(this.responseBuffers)
          }
        }
      })
    })
  }

  async getStatus() {
    const responseData = await this.getResponseData()

    try {
      return JSON.parse(responseData.toString())
    } catch (error) {
      console.log(responseData.toString())
      return {}
    }
  }

  /** @return {Promise<{host: string, ip: string, port: string}>} */
  getDebugInfo() {
    if (this.debugInfo) return Promise.resolve(this.debugInfo)

    this.socket = new Socket().connect({ host: this.host, port: this.port })

    return new Promise((resolve) => {
      this.socket.on('connect', () => {
        this.debugInfo = {
          host: this.host,
          ip: this.socket.remoteAddress || this.host,
          port: this.socket.remotePort || this.port,
        }

        this.socket.destroy()

        resolve(this.debugInfo)
      })
    })
  }

  /** @param {Uint8Array[]} arrays */
  static concatData(arrays) {
    const totalLength = arrays.reduce((acc, value) => acc + value.length, 0)
    let result = new Uint8Array(totalLength)

    arrays.reduce((offset, arr) => {
      result.set(arr, offset)
      return offset + arr.length
    }, 0)

    return result
  }

  /** @param {number} num */
  static packVarint(num) {
    const buffers = []

    while (true) {
      if (num > 0x7f) {
        buffers.push(0x80 | (num & 0x7f))
        num >>= 7
      } else {
        buffers.push(num)
        break
      }
    }

    return Uint8Array.from(buffers)
  }

  /** @param {Socket} socket */
  static unPackVarint(socket) {
    let result = 0

    for (let idx = 0; idx < 5; idx++) {
      let bufferVal = socket.read(1)[0]

      result |= (bufferVal & 0x7f) << (idx * 7)

      if ((bufferVal & 0x80) === 0) return result
    }

    return result
  }
}

async function start() {
  const server = new MineStatus('mc.hypixel.net', 25565)
  console.log(await server.getStatus())
}

start()