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'use strict'; | |
const process = require('process'); | |
const dgram = require('dgram'); | |
// Command line args: | |
let [listenport, fwdport, fwdaddr, mindelay, maxdelay] = process.argv.slice(2); | |
// It will listen on <listenport> and act as a reverse proxy for the UDP service | |
// at <fwdaddr>:<fwdport>. All packets will be delayed by a uniformly | |
// distributed random value between <mindelay> and <maxdelay> in milleseconds. | |
// Defaults: | |
listenport = Number(listenport) || 30001; | |
fwdport = Number(fwdport) || 30000; | |
fwdaddr = fwdaddr || '127.0.0.1'; | |
mindelay = Number(mindelay) || 400; | |
maxdelay = Number(maxdelay) || (mindelay * 1.25); | |
console.log(`${listenport}->${fwdaddr}:${fwdport} min ${mindelay} max ${maxdelay}`); | |
function delaysend(sock, msg, toport, toaddr, fromport, fromaddr) { | |
const delay = Math.floor(Math.random() * (maxdelay - mindelay) + mindelay); | |
setTimeout(() => sock.send(msg, toport, toaddr), delay); | |
} | |
const server = dgram.createSocket('udp4'); | |
server.on('error', e => { throw e; }); | |
server.on('listening', () => `listening on ${listenport}`); | |
server.bind(listenport); | |
const fwds = {}; | |
server.on('message', (msg, info) => { | |
const { address, port } = info; | |
const key = `${address}:${port}`; | |
let sock = fwds[key]; | |
if(!sock) { | |
fwds[key] = sock = dgram.createSocket('udp4'); | |
sock.on('error', e => { throw e; }); | |
server.on('listening', () => console.log(`new connection from ${address}:${port | |
} relaying via port ${sock.address().port}`)); | |
sock.on('message', m => delaysend(server, m, port, address, fwdport, fwdaddr)); | |
} | |
delaysend(sock, msg, fwdport, fwdaddr, port, address); | |
}); |
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