feat: add STUN/TURN server support and environment config

- Extended .gitignore to exclude .env files containing sensitive info.
- Imported `crypto` module and added route to generate TURN credentials.
- Enhanced upload/download functionality to use STUN/TURN servers.
- Improved UI text for upload/download scenarios for clarity.
- Added fetching of TURN credentials in the client to enable P2P connections.

These changes improve file sharing reliability by providing fallbacks for network traversal.

.gitignore

@@ -1 +1,2 @@
-node_modules/
+node_modules/
+.env

app.js

@@ -2,12 +2,17 @@ import express from 'express';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import bip39 from 'bip39';
+import crypto from 'crypto';
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 
 const app = express();
 const trackerUrl = process.env.TRACKER_URL || 'ws://localhost:8106';
+const stunServerUrl = process.env.STUN_SERVER_URL;
+const turnServerUrl = process.env.TURN_SERVER_URL;
+const turnSecret = process.env.TURN_SECRET;
+const turnTTL = 86400;
 
 app.set('view engine', 'ejs');
 app.use(express.static(path.join(__dirname, 'public')));
@@ -28,6 +33,30 @@ app.get('/get-infohash/:mnemonic', (req, res) => {
     res.json({ infoHash });
 });
 
+app.get('/turn-credentials', (req, res) => {
+    const iceServers = [];
+
+    if (stunServerUrl) {
+        iceServers.push({ urls: stunServerUrl });
+    }
+
+    if (turnServerUrl && turnSecret) {
+        const unixTimeStamp = Math.floor(Date.now() / 1000) + turnTTL;
+        const username = `${unixTimeStamp}:transfercoffee`;
+        const hmac = crypto.createHmac('sha1', turnSecret);
+        hmac.update(username);
+        const credential = hmac.digest('base64');
+
+        iceServers.push({
+            urls: turnServerUrl,
+            username: username,
+            credential: credential
+        });
+    }
+
+    res.json({ iceServers });
+});
+
 const PORT = process.env.PORT || 8105;
 app.listen(PORT, () => {
     console.log(`Server is running on port ${PORT}`);

public/js/index.js

@@ -1,6 +1,13 @@
 const client = new WebTorrent();
+const trackerUrl = "<%= trackerUrl %>";
 
-function uploadFile() {
+async function getRTCIceServers() {
+  const response = await fetch("/turn-credentials");
+  const data = await response.json();
+  return data.iceServers;
+}
+
+async function uploadFile() {
   const fileInput = document.getElementById("fileInput");
   const file = fileInput.files[0];
   const uploadProgressBar = document.getElementById("uploadProgressBar");
@@ -10,8 +17,13 @@ function uploadFile() {
     return;
   }
 
+  const rtcConfig = {
+    iceServers: await getRTCIceServers(),
+  };
+
   const opts = {
     announce: [trackerUrl],
+    rtcConfig: rtcConfig,
   };
 
   client.seed(file, opts, (torrent) => {
@@ -19,9 +31,8 @@ function uploadFile() {
       .then((response) => response.json())
       .then((data) => {
         const uploadResult = document.getElementById("uploadResult");
-        uploadResult.innerHTML = `Started sharing file. Share this mnemonic: <strong>${data.mnemonic}</strong>
-        <br>Note that the file will be available for download as long as this page is open.
-        `;
+        uploadResult.innerHTML = `<p>Sharing your file. Share this mnemonic: <strong>${data.mnemonic}</strong></p>
+        <p>The file will be available for download as long as you keep this page open.</p>`;
       });
 
     torrent.on("upload", () => {
@@ -32,7 +43,7 @@ function uploadFile() {
   });
 }
 
-function downloadFile() {
+async function downloadFile() {
   const mnemonicInput = document.getElementById("mnemonicInput").value;
   const downloadProgressBar = document.getElementById("downloadProgressBar");
 
@@ -41,6 +52,10 @@ function downloadFile() {
     return;
   }
 
+  const rtcConfig = {
+    iceServers: await getRTCIceServers(),
+  };
+
   fetch(`/get-infohash/${mnemonicInput}`)
     .then((response) => response.json())
     .then((data) => {
@@ -48,6 +63,7 @@ function downloadFile() {
 
       const opts = {
         announce: [trackerUrl],
+        rtcConfig: rtcConfig,
       };
 
       client.add(torrentId, opts, (torrent) => {

views/index.ejs

@@ -18,9 +18,9 @@
         <div class="result" id="uploadResult"></div>
       </div>
       <div class="section">
-        <h2>Download File</h2>
+        <h2>Receive File</h2>
         <input type="text" id="mnemonicInput" placeholder="Enter mnemonic" />
-        <button onclick="downloadFile()">Download</button>
+        <button onclick="downloadFile()">Receive</button>
         <div class="progress" id="downloadProgress">
           <div class="progress-bar" id="downloadProgressBar">0%</div>
         </div>