send data file to another computer with RTCPeerConnection?

how can I change the code so that the computer1 code connects to the code of computer 2(computer1 and computer2 are not the same computers but on the same network).

It works locally but not when it’s two different computers

computer 1 and computer2 code that is used for the connection is defined below

this is the code that does the networking on computer1

async function createConnection() {
  abortButton.disabled = false;
  sendFileButton.disabled = true;

  localConnection = new RTCPeerConnection();//this is the line I think I need to change

  console.log('Created local peer connection object localConnection');

  sendChannel = localConnection.createDataChannel('sendDataChannel');
  sendChannel.binaryType = 'arraybuffer';
  console.log('Created send data channel');

  sendChannel.addEventListener('open', onSendChannelStateChange);
  sendChannel.addEventListener('close', onSendChannelStateChange);
  sendChannel.addEventListener('error', onError);

  localConnection.addEventListener('icecandidate', async event => {
    console.log('Local ICE candidate: ', event.candidate);
    await localConnection.addIceCandidate(event.candidate);
  });

this is the part of the program that have the role to receive the request and the file data on the computer2

async function server(){
  remoteConnection = new RTCPeerConnection();

    alert("start");
    console.log('Created remote peer connection object remoteConnection');

    remoteConnection.addEventListener('icecandidate', async event => {
      console.log('Remote ICE candidate: ', event.candidate);
      await localConnection.addIceCandidate(event.candidate);
    });
    remoteConnection.addEventListener('datachannel', receiveChannelCallback);

}

the code that I modified(main.js)

/* eslint no-unused-expressions: 0 */
/*
 *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
'use strict';

let localConnection;
let remoteConnection;
let sendChannel;
let receiveChannel;
let fileReader;
const bitrateDiv = document.querySelector('div#bitrate');
const fileInput = document.querySelector('input#fileInput');
const abortButton = document.querySelector('button#abortButton');
const downloadAnchor = document.querySelector('a#download');
const sendProgress = document.querySelector('progress#sendProgress');
const receiveProgress = document.querySelector('progress#receiveProgress');
const statusMessage = document.querySelector('span#status');
const sendFileButton = document.querySelector('button#sendFile');

let receiveBuffer = [];
let receivedSize = 0;

let bytesPrev = 0;
let timestampPrev = 0;
let timestampStart;
let statsInterval = null;
let bitrateMax = 0;
server();

sendFileButton.addEventListener('click', () => createConnection());
fileInput.addEventListener('change', handleFileInputChange, false);
abortButton.addEventListener('click', () => {
  if (fileReader && fileReader.readyState === 1) {
    console.log('Abort read!');
    fileReader.abort();
  }
});

async function handleFileInputChange() {
  const file = fileInput.files[0];
  if (!file) {
    console.log('No file chosen');
  } else {
    sendFileButton.disabled = false;
  }
}
async function server(){
  //const servers = {
  //iceServers: [
  //  {
  //    urls: ['stun:stun1.l.google.com:19302', //'stun:stun2.l.google.com:19302'],
  //  },
  //],
  //iceCandidatePoolSize: 10,
//};
  remoteConnection = new RTCPeerConnection();
  
    alert("start");
    console.log('Created remote peer connection object remoteConnection');

    remoteConnection.addEventListener('icecandidate', async event => {
      console.log('Remote ICE candidate: ', event.candidate);
      await localConnection.addIceCandidate(event.candidate);
    });
    remoteConnection.addEventListener('datachannel', receiveChannelCallback);

}
async function createConnection() {
  abortButton.disabled = false;
  sendFileButton.disabled = true;
  //const servers = {
  //iceServers: [
  //  {
  //    urls: ['stun:stun1.l.google.com:19302', //'stun:stun2.l.google.com:19302'],
 //   },
  //],
  //iceCandidatePoolSize: 10,
//};
  
  localConnection = new RTCPeerConnection();
  
  console.log('Created local peer connection object localConnection');

  sendChannel = localConnection.createDataChannel('sendDataChannel');
  sendChannel.binaryType = 'arraybuffer';
  console.log('Created send data channel');

  sendChannel.addEventListener('open', onSendChannelStateChange);
  sendChannel.addEventListener('close', onSendChannelStateChange);
  sendChannel.addEventListener('error', onError);

  localConnection.addEventListener('icecandidate', async event => {
    console.log('Local ICE candidate: ', event.candidate);
    await localConnection.addIceCandidate(event.candidate);
  });

  
  try {
    const offer = await localConnection.createOffer();
    await gotLocalDescription(offer);
  } catch (e) {
    console.log('Failed to create session description: ', e);
  }

  fileInput.disabled = true;
}

function sendData() {
  const file = fileInput.files[0];
  console.log(`File is ${[file.name, file.size, file.type, file.lastModified].join(' ')}`);

  // Handle 0 size files.
  statusMessage.textContent = '';
  downloadAnchor.textContent = '';
  if (file.size === 0) {
    bitrateDiv.innerHTML = '';
    statusMessage.textContent = 'File is empty, please select a non-empty file';
    closeDataChannels();
    return;
  }
  sendProgress.max = file.size;
  receiveProgress.max = file.size;
  const chunkSize = 16384;
  fileReader = new FileReader();
  let offset = 0;
  fileReader.addEventListener('error', error => console.error('Error reading file:', error));
  fileReader.addEventListener('abort', event => console.log('File reading aborted:', event));
  fileReader.addEventListener('load', e => {
    console.log('FileRead.onload ', e);
    sendChannel.send(e.target.result);
    offset += e.target.result.byteLength;
    sendProgress.value = offset;
    if (offset < file.size) {
      readSlice(offset);
    }
  });
  const readSlice = o => {
    console.log('readSlice ', o);
    const slice = file.slice(offset, o + chunkSize);
    fileReader.readAsArrayBuffer(slice);
  };
  readSlice(0);
}

function closeDataChannels() {
  console.log('Closing data channels');
  sendChannel.close();
  console.log(`Closed data channel with label: ${sendChannel.label}`);
  sendChannel = null;
  if (receiveChannel) {
    receiveChannel.close();
    console.log(`Closed data channel with label: ${receiveChannel.label}`);
    receiveChannel = null;
  }
  localConnection.close();
  remoteConnection.close();
  localConnection = null;
  remoteConnection = null;
  console.log('Closed peer connections');

  // re-enable the file select
  fileInput.disabled = false;
  abortButton.disabled = true;
  sendFileButton.disabled = false;
}

async function gotLocalDescription(desc) {
  await localConnection.setLocalDescription(desc);
  console.log(`Offer from localConnectionn ${desc.sdp}`);
  await remoteConnection.setRemoteDescription(desc);
  try {
    const answer = await remoteConnection.createAnswer();
    await gotRemoteDescription(answer);
  } catch (e) {
    console.log('Failed to create session description: ', e);
  }
}

async function gotRemoteDescription(desc) {
  await remoteConnection.setLocalDescription(desc);
  console.log(`Answer from remoteConnectionn ${desc.sdp}`);
  await localConnection.setRemoteDescription(desc);
}

function receiveChannelCallback(event) {
  console.log('Receive Channel Callback');
  receiveChannel = event.channel;
  receiveChannel.binaryType = 'arraybuffer';
  receiveChannel.onmessage = onReceiveMessageCallback;
  receiveChannel.onopen = onReceiveChannelStateChange;
  receiveChannel.onclose = onReceiveChannelStateChange;

  receivedSize = 0;
  bitrateMax = 0;
  downloadAnchor.textContent = '';
  downloadAnchor.removeAttribute('download');
  if (downloadAnchor.href) {
    URL.revokeObjectURL(downloadAnchor.href);
    downloadAnchor.removeAttribute('href');
  }
}

function onReceiveMessageCallback(event) {
  console.log(`Received Message ${event.data.byteLength}`);
  receiveBuffer.push(event.data);
  receivedSize += event.data.byteLength;
  receiveProgress.value = receivedSize;

  // we are assuming that our signaling protocol told
  // about the expected file size (and name, hash, etc).
  const file = fileInput.files[0];
  if (receivedSize === file.size) {
    const received = new Blob(receiveBuffer);
    receiveBuffer = [];

    downloadAnchor.href = URL.createObjectURL(received);
    downloadAnchor.download = file.name;
    downloadAnchor.textContent =
      `Click to download '${file.name}' (${file.size} bytes)`;
    downloadAnchor.style.display = 'block';

    const bitrate = Math.round(receivedSize * 8 /
      ((new Date()).getTime() - timestampStart));
    bitrateDiv.innerHTML =
      `<strong>Average Bitrate:</strong> ${bitrate} kbits/sec (max: ${bitrateMax} kbits/sec)`;

    if (statsInterval) {
      clearInterval(statsInterval);
      statsInterval = null;
    }

    closeDataChannels();
  }
}

function onSendChannelStateChange() {
  if (sendChannel) {
    const {readyState} = sendChannel;
    console.log(`Send channel state is: ${readyState}`);
    if (readyState === 'open') {
      sendData();
    }
  }
}

function onError(error) {
  if (sendChannel) {
    console.error('Error in sendChannel:', error);
    return;
  }
  console.log('Error in sendChannel which is already closed:', error);
}

async function onReceiveChannelStateChange() {
  if (receiveChannel) {
    const readyState = receiveChannel.readyState;
    console.log(`Receive channel state is: ${readyState}`);
    if (readyState === 'open') {
      timestampStart = (new Date()).getTime();
      timestampPrev = timestampStart;
      statsInterval = setInterval(displayStats, 500);
      await displayStats();
    }
  }
}

// display bitrate statistics.
async function displayStats() {
  if (remoteConnection && remoteConnection.iceConnectionState === 'connected') {
    const stats = await remoteConnection.getStats();
    let activeCandidatePair;
    stats.forEach(report => {
      if (report.type === 'transport') {
        activeCandidatePair = stats.get(report.selectedCandidatePairId);
      }
    });
    if (activeCandidatePair) {
      if (timestampPrev === activeCandidatePair.timestamp) {
        return;
      }
      // calculate current bitrate
      const bytesNow = activeCandidatePair.bytesReceived;
      const bitrate = Math.round((bytesNow - bytesPrev) * 8 /
        (activeCandidatePair.timestamp - timestampPrev));
      bitrateDiv.innerHTML = `<strong>Current Bitrate:</strong> ${bitrate} kbits/sec`;
      timestampPrev = activeCandidatePair.timestamp;
      bytesPrev = bytesNow;
      if (bitrate > bitrateMax) {
        bitrateMax = bitrate;
      }
    }
  }
}

Thanks for helping

Answer

You can read about peer connections where every peer connection is handled by the RTCPeerConnection object and it defines how the peer connection is set up and how it should include the information about the ICE servers to use.
You can define the ICE servers as following:

  localConnection = new RTCPeerConnection({iceServers: [{ url: "stun:"+ ip +":8003" }]})

or

  localConnection = new RTCPeerConnection({iceServers: [{ url: + ip + ':port' }]})

or

      var servers = {
    iceTransportPolicy: 'relay',
    iceServers: [{
      urls: "turn:[" + ip + "]:3478",
      username: "username", 
      credential: "password"
    }
  ]};
  var localConnection = new RTCPeerConnection(servers);

Moreover, You can find the full code here or here under the folder name filetransfer .