Requirements

Before installing AudioLink, make sure you have the following in place.

Server (VPS)

• Node.js 20 LTS — download from nodejs.org
• A VPS running Ubuntu 20.04, 22.04 or 24.04 (any Linux distro works)
• Port 8765 open in your firewall (TCP)
• A dedicated IP address — shared hosting will not work

TX Computer (Studio)

• Windows, macOS or Linux
• Chrome or Edge browser (latest version)
• An audio input device — microphone, USB audio interface, or virtual cable
• Stable internet connection with at least 3 Mbps upload (16-bit mode) or 6 Mbps upload (32-bit Float mode)

RX Computer (Destination)

• Windows, macOS or Linux
• Chrome or Edge browser (latest version)
• A audio output device (speakers or headphones)
• Stable internet connection with at least 3 Mbps download

Installation

Installing AudioLink on your VPS takes about 10 minutes. Everything runs as a single Node.js process — no web server, no database, no complex setup.

Step 1 — Connect to your VPS

ssh root@YOUR.VPS.IP.ADDRESS

Step 2 — Install Node.js

curl -fsSL https://deb.nodesource.com/setup_20.x | sudo -E bash -
sudo apt-get install -y nodejs

Verify it installed correctly:

node --version
npm --version

Step 3 — Create the AudioLink folder

mkdir -p /opt/audiolink
cd /opt/audiolink

Step 4 — Upload the files

Upload server.js, tx.html, rx.html and config.json to /opt/audiolink/ using WinSCP or SCP.

Step 5 — Install the WebSocket dependency

cd /opt/audiolink
npm install ws

Step 6 — Open the firewall port

# If using UFW:
sudo ufw allow 8765/tcp

# If using iptables:
sudo iptables -A INPUT -p tcp --dport 8765 -j ACCEPT
sudo iptables-save | sudo tee /etc/iptables/rules.v4

Step 7 — Start the server

node server.js

You should see the server start and print the TX and RX URLs. Open http://YOUR.VPS.IP:8765/tx in your browser to confirm it works.

config.json

All settings for the AudioLink server are in a single file — config.json — located in the same folder as server.js. Edit this file before starting the server.

{
  "username": "admin",
  "password": "changeme123",
  "port": 8765,
  "https_port": 8766,
  "station_name": "My Radio Station",
  "ssl_cert": "",
  "ssl_key": ""
}

Settings reference

After editing config.json, restart the server for changes to take effect:

pm2 restart audiolink

TX — Transmitter

The TX page is where you capture and transmit audio. Open it on the studio computer at:

http://YOUR.VPS.IP:8765/tx

Connecting to the server

Enter the WebSocket URL in the Server section:

ws://YOUR.VPS.IP:8765

Enter your station label and click CONNECT. The status shows CONNECTED when the server is reached.

Selecting your audio source

AudioLink automatically scans your audio devices and selects the best one. Devices are scored and ranked — professional audio interfaces and virtual cables are preferred over built-in microphones. The device quality badge shows what was detected.

If the wrong device is selected, choose the correct one from the Source Device dropdown and click ↻ SCAN to refresh the list.

Audio settings

Monitoring before going live

Click MONITOR AUDIO to open your audio input and start the meters without transmitting. Use this to check levels before the broadcast:

• Signal — confirms audio is reaching AudioLink
• No Clip — warns if you are hitting 0 dBFS
• Stereo — confirms both channels are present and balanced
• Level OK — green when signal is in the broadcast sweet spot (−18 to −6 dBFS)

Adjust the Input Gain slider until all four checks show green, then click GO LIVE.

Going live

Click GO LIVE. The ON AIR badge appears with a live elapsed timer. The same audio pipeline that was already running for monitoring starts transmitting immediately — no gap, no click.

Click END BROADCAST to stop transmitting. AudioLink returns to monitoring mode, keeping the audio pipeline open so you can check levels again before your next segment.

RX — Receiver

The RX page receives and plays the audio stream. Open it on the destination computer at:

http://YOUR.VPS.IP:8765/rx

Connecting

Enter the same WebSocket URL as TX:

ws://YOUR.VPS.IP:8765

Click CONNECT. When TX is broadcasting, a banner appears showing the TX station name and audio configuration.

Buffer size

Choose the buffer size based on your network stability:

For a 24/7 broadcast over the internet, 150 ms or 300 ms is recommended. The extra buffer absorbs network jitter and prevents dropouts.

Starting playback

Click START PLAYBACK. The RX engine pre-buffers audio to the target level before starting output — you will see BUFFERING 0%…100% then PLAYING. This pre-buffer phase ensures smooth, glitch-free playback from the first second.

Monitoring playback health

• Buffer Health — should stay above 50% (green). If it drops to red frequently, increase the buffer size.
• Dropouts — occasional dropouts are normal. Many dropouts indicate a network issue — run the speed test.
• Buf Lat — current audio in buffer in milliseconds. Should be close to your chosen buffer size.

Audio sounds slow or distorted

This is caused by a sample rate mismatch between the TX and the RX browser. Fix: on the TX page, change the Sample Rate to 44100 Hz. This matches most browsers' native audio rate and eliminates the mismatch entirely.

VB-Audio Virtual Cable

If your studio computer runs automation software like RadioBOSS, you can route its audio output directly into AudioLink TX using a free virtual audio cable — no physical cable or audio interface required.

What is a virtual audio cable?

A virtual audio cable creates two virtual devices in Windows — a virtual speaker (CABLE Input) and a virtual microphone (CABLE Output). Audio sent to the virtual speaker reappears on the virtual microphone. This lets you route audio between applications internally.

Installation

1. Download VB-Audio Virtual Cable (free) from vb-audio.com/Cable
2. Run the installer as Administrator
3. Restart Windows when prompted

Setting up RadioBOSS

1. Open RadioBOSS → Settings → Options → Sound Devices
2. Set Output Device to CABLE Input (VB-Audio Virtual Cable)
3. Click OK

Setting up AudioLink TX

1. On the TX page, the Source Device dropdown automatically detects and prefers VB-Audio Cable Output
2. Select CABLE Output (VB-Audio Virtual Cable) if it is not already selected
3. The device quality badge shows Virtual cable — capture system audio
4. Click MONITOR AUDIO — meters should show RadioBOSS audio

Other virtual cable options

• VB-Audio (Windows) — free, most common, recommended
• BlackHole (macOS) — free, works the same way
• Stereo Mix — built into some Windows audio drivers, captures all system audio

Network Speed Test

AudioLink includes a built-in 3-phase network test that measures whether your connection can reliably sustain a live broadcast. Run it before going live to diagnose potential issues.

Running the test

Click RUN TEST on either the TX or RX page. You must be connected to the server first. The test takes about 10 seconds and runs three phases automatically.

What it measures

Interpreting results

• High jitter — packets arrive unevenly. Increase the RX buffer size to compensate.
• Low throughput — your connection cannot sustain the full bitrate. Switch to 16-bit Int mode on TX to reduce bandwidth.
• Packet loss above 0% — some packets are being dropped in transit. This will cause audio dropouts. Try a different network or contact your ISP.

Running 24/7 with PM2

PM2 is a process manager for Node.js. It keeps AudioLink running after you close SSH, restarts it automatically if it crashes, and starts it again after a server reboot.

Installing PM2

sudo npm install -g pm2

Starting AudioLink with PM2

cd /opt/audiolink
pm2 start server.js --name audiolink

Auto-start on server reboot

# Generate and run the startup command
pm2 startup
# Copy and run the command it prints, then:
pm2 save

Daily PM2 commands

pm2 status              # Check if AudioLink is running
pm2 logs audiolink      # View live logs
pm2 restart audiolink   # Restart the server
pm2 stop audiolink      # Stop the server
pm2 start audiolink     # Start again

Keeping firewall rules after reboot

sudo apt install iptables-persistent -y
sudo netfilter-persistent save

This saves your iptables rules so port 8765 stays open after every reboot.

SSL / HTTPS Setup

Running AudioLink over HTTPS and WSS is required when accessing the TX or RX pages from a domain with an SSL certificate. It also permanently resolves the browser microphone permission issue.

Getting an SSL certificate

If you have a domain pointing to your VPS, use Certbot to get a free Let's Encrypt certificate:

sudo apt install certbot -y
certbot certonly --standalone -d yourdomain.com

Configuring SSL in config.json

{
  "ssl_cert": "/etc/letsencrypt/live/yourdomain.com/fullchain.pem",
  "ssl_key":  "/etc/letsencrypt/live/yourdomain.com/privkey.pem"
}

Restart AudioLink after saving. The server now serves HTTPS on port 8766 and WSS for WebSocket connections.

Accessing the pages over HTTPS

https://yourdomain.com:8766/tx    ← TX page
https://yourdomain.com:8766/rx    ← RX page
wss://yourdomain.com:8766         ← WebSocket URL in TX and RX

Behind Nginx (optional)

If you run Nginx on the same server, you can proxy AudioLink through a subdomain. Create a new Nginx server block — do not modify your existing site's config:

server {
    listen 443 ssl;
    server_name audio.yourdomain.com;

    ssl_certificate /etc/letsencrypt/live/audio.yourdomain.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/audio.yourdomain.com/privkey.pem;

    location / {
        proxy_pass http://127.0.0.1:8765;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_read_timeout 3600s;
    }
}

Chrome Mic Permission

Chrome requires microphone permission for AudioLink TX to capture audio. This permission is granted once and remembered permanently — but only when the page is served over a trusted origin.

When Chrome asks for permission

The first time you click MONITOR AUDIO, Chrome shows a permission popup. Click Allow while visiting the site. Chrome will not ask again for this origin.

If Chrome blocks the microphone on HTTP

Chrome only remembers microphone permissions for HTTPS origins and localhost. If you access TX over plain HTTP with an IP address (e.g. http://185.67.45.7:8765), Chrome may ask every time or block it entirely.

Fix — Chrome flag (temporary):

1. Open Chrome and go to: chrome://flags/#unsafely-treat-insecure-origin-as-secure
2. In the text box, type your TX URL: http://YOUR.VPS.IP:8765
3. Set the dropdown to Enabled
4. Click Relaunch

Permanent fix: Set up SSL as described in Chapter 10. Once the TX page is served over HTTPS, Chrome remembers the permission permanently with no further steps.

Troubleshooting

Audio sounds slow or in slow motion

Cause: Sample rate mismatch. TX is sending at 48000 Hz but the RX browser's native rate is 44100 Hz.

Fix: On the TX page, change Sample Rate to 44100 Hz. Stop and restart the broadcast. The audio will play at the correct speed.

To check your audio device's native rate on Windows: right-click the speaker icon → Sound Settings → Recording → your device → Properties → Advanced.

Audio cutting out / many dropouts

• Increase the Buffer Size on RX to 150ms or 300ms
• Run the Network Speed Test — check for packet loss above 0% or jitter above 5ms
• Switch to 16-bit Int on TX to halve the bandwidth requirement
• If TX and RX are on the same internet connection, the combined bandwidth (upload + download) may exceed the connection's stable throughput

Unable to load a worklet's module

Cause: Chrome blocks AudioWorklet from certain URL types.

Fix: Access the TX page via http:// (served from the Node.js server), not by opening the HTML file directly from your filesystem. The server URL is http://YOUR.VPS.IP:8765/tx.

TX connects but RX shows no TX online

• Confirm both TX and RX are connected to the same WebSocket URL
• Check pm2 status — confirm audiolink is online
• Check pm2 logs audiolink for error messages

Page not loading at all

• Confirm port 8765 is open in your firewall
• Check if your VPS provider has a separate cloud-level firewall (DigitalOcean, Hetzner, AWS security groups)
• Run pm2 status to confirm the server is running

Microphone permission denied

See Chapter 11 — Chrome Mic Permission for the complete fix.

Still stuck? Contact support@soundcast.ca — include a description of your setup, the browser console errors (F12 → Console), and what you see on screen.

Free vs Pro Edition

A complete summary of what is included in each edition.

The Pro edition is coming soon. Join the waitlist to be notified at launch.