duplicate.js

const fetch_count = 16;
const srcRelay = 'ws://localhost:8080'
const dstRelay = 'ws://localhost:8888'

let srcSocket;
let dstSocket;
let until = (new Date()) / 1000;
if (typeof (WebSocket) === 'undefined') {
  const WebSocket = require('websocket').w3cwebsocket
  srcSocket = new WebSocket(srcRelay)
  dstSocket = new WebSocket(dstRelay)
} else {
  srcSocket = new WebSocket(srcRelay)
  dstSocket = new WebSocket(dstRelay)
}

srcSocket.onopen = () => {
  console.log('Destination Websocket is open.')
  dstSocket.onopen = () => {
    console.log('Source Websocket is open.')

    srcSocket.send(JSON.stringify(['REQ', crypto.randomUUID(), {
      limit: fetch_count
    }]))
  }
}

dstSocket.onmessage = (message) => {
  console.log('Destination Websocket: ', message.data);
}

srcSocket.onmessage = (message) => {
  const event = JSON.parse(message.data);
  if (event[0] === 'EOSE') {
    srcSocket.send(JSON.stringify(["CLOSE", event[1]]));
    console.log(`until = ${until}`)
    const req = ['REQ', crypto.randomUUID(), {
      until: until,
      limit: fetch_count
    }];
    console.log(JSON.stringify(req));
    setTimeout(() => {
      srcSocket.send(JSON.stringify(req));
    }, 200);
  } else if (event[0] === 'EVENT' ) {
    const e = event[2]
    if ( e.created_at < until ) {
      until = e.created_at;
    }
    console.log(JSON.stringify(e.id))
    dstSocket.send(JSON.stringify(['EVENT', e]))
  }
}

dstSocket.onclose = () => {
  console.log('Destination Websocket is closed.')
}
dstSocket.onerror = (e) => {
  console.log('Destination Websocket encountered error: ', e)
}
srcSocket.onclose = () => {
  console.log('Source Websocket is closed.')
}
srcSocket.onerror = (e) => {
  console.log('Source Websocket encountered error: ', e)
}