mineping/lib/java.js

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/**
* Implementation of the Java Minecraft ping protocol.
* @see https://wiki.vg/Server_List_Ping
*/
'use strict';
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import net from 'node:net';
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import varint from './varint.js';
/**
* Ping a Minecraft Java server.
* @param {string} host The host of the Java server.
* @param {number} [port=25565] The port of the Java server.
* @param {function} cb The callback function to handle the ping response.
* @param {number} [timeout=5000] The timeout duration in milliseconds.
* @param {number} [protocolVersion=-1] The protocol version of the Java client.
*/
function ping(host, port = 25565, cb, timeout = 5000, protocolVersion = -1) {
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const socket = net.createConnection(({ host, port }));
// Set manual timeout interval.
// This ensures the connection will NEVER hang regardless of internal state
const timeoutTask = setTimeout(() => {
socket.emit('error', new Error('Socket timeout'));
}, timeout);
const closeSocket = () => {
socket.destroy();
clearTimeout(timeoutTask);
};
// Generic error handler
// This protects multiple error callbacks given the complex socket state
// This is mostly dangerous since it can swallow errors
let didFireError = false;
/**
* Handle any error that occurs during the ping process.
* @param {Error} err The error that occurred.
*/
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const handleError = (err) => {
closeSocket();
if (!didFireError) {
didFireError = true;
cb(null, err);
}
};
// #setNoDelay instantly flushes data during read/writes
// This prevents the runtime from delaying the write at all
socket.setNoDelay(true);
socket.on('connect', () => {
const handshake = varint.concat([
varint.encodeInt(0),
varint.encodeInt(protocolVersion),
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varint.encodeInt(host.length),
varint.encodeString(host),
varint.encodeUShort(port),
varint.encodeInt(1)
]);
socket.write(handshake);
const request = varint.concat([
varint.encodeInt(0)
]);
socket.write(request);
});
let incomingBuffer = Buffer.alloc(0);
socket.on('data', (data) => {
incomingBuffer = Buffer.concat([incomingBuffer, data]);
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// Wait until incomingBuffer is at least 5 bytes long to ensure it has captured the first VarInt value
// This value is used to determine the full read length of the response
// "VarInts are never longer than 5 bytes"
// https://wiki.vg/Data_types#VarInt_and_VarLong
if (incomingBuffer.length < 5) {
return;
}
let offset = 0;
const packetLength = varint.decodeInt(incomingBuffer, offset);
// Ensure incomingBuffer contains the full response
if (incomingBuffer.length - offset < packetLength) {
return;
}
const packetId = varint.decodeInt(incomingBuffer, varint.decodeLength(packetLength));
if (packetId === 0) {
const data = incomingBuffer.subarray(varint.decodeLength(packetLength) + varint.decodeLength(packetId));
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const responseLength = varint.decodeInt(data, 0);
const response = data.subarray(varint.decodeLength(responseLength), varint.decodeLength(responseLength) + responseLength);
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try {
const message = JSON.parse(response);
closeSocket();
cb(message, null);
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} catch (err) {
handleError(err);
}
} else {
handleError(new Error('Received unexpected packet'));
}
});
socket.on('error', handleError);
}
/**
* Asynchronously ping Minecraft Java server.
* The optional `options` argument can be an object with a `port` (default is `25565`) or/and `timeout` (default is `5000`) or/and `protocolVersion` (default is `-1`) property.
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* @param {string} host The Java server address.
* @param {import('../types/index.js').PingOptions} options The configuration for pinging Minecraft Java server.
* @returns {Promise<import('../types/index.js').JavaPingResponse>}
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*/
export function pingJava(host, options = {}) {
if (!host) throw new Error('Host argument is not provided');
const { port = 25565, timeout = 5000, protocolVersion = -1 } = options;
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return new Promise((resolve, reject) => {
ping(host, port, (res, err) => {
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err ? reject(err) : resolve(res);
}, timeout, protocolVersion);
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});
}