Radioteletype Presentation

Live project: radioteletype.net

Browser Radio
for private communication

Radioteletype connects two users through WebRTC with live audio, video, chat, screen sharing, and direct file transfer.

Purpose

Fast communication.
Minimal identity.

The goal is a stateless peer-to-peer communication experience: no accounts, no database, and no message history.

WebSockets introduces peers.

WebRTC
carries data.

Radioteletype uses both because they solve different problems: one coordinates the connection, the other moves real-time media and data between browsers.

WebSocket A persistent browser-to-server connection. In this project it is the signaling line for room matching, offers, answers, and ICE candidates.

WebRTC A browser-to-browser real-time connection. It carries encrypted audio, video, chat, screen share, and X-FTP data channels.

Why both? Browsers need help finding each other first. After that, WebRTC can take over and avoid sending media through the backend.

Backend role The server stays lightweight: it coordinates setup, but it does not store accounts, messages, files, or call history.

Most important code

The backend assigns roles.
The frontend starts WebRTC.

The backend decides who creates the offer. The frontend receives that role through WebSocket signaling and starts the peer connection.

Backend pairing

service.pair(ws, peer)

send(ws, {
  type: 'peer-found',
  peerId: peer.id,
  initiator: true,
})

send(peer, {
  type: 'peer-found',
  peerId: ws.id,
  initiator: false,
})

Pairs two sockets and gives only one browser permission to create the WebRTC offer.

Frontend signaling

if (msg.type === 'peer-found') {
  if (!pc && msg.initiator) {
    await startPeer(true, msg.peerId)
  }
}

if (isInitiator) {
  const offer = await pc.createOffer()
  await pc.setLocalDescript(offer)
  safeSend({ type: 'offer', target: peerId, sdp: offer })
}

Reads the backend role, starts the peer connection, and sends the offer through WebSocket signaling.

Connection flow

Simple connection flow

The backend helps two browsers find each other. After the handshake, the session moves into WebRTC for real-time communication.

Direct vs relay

STUN discovers.
TURN relays.

Direct Mode is preferred because media travels peer-to-peer. Relay Mode exists for networks where NAT or firewalls block that direct route.

VPS deployment

Self-hosted infrastructure
was part of
the work.

The project runs on a configured VPS using Nginx, PM2, HTTPS/WSS, and a coturn relay server for difficult networks.

coturn configuration

TLS-only TURN relay
for blocked networks.

coturn runs on the VPS as the fallback relay when two browsers cannot establish a direct peer-to-peer path.

/etc/turnserver.conf

# TURN SERVER CONFIG (TLS ONLY)
# =============================

# --- Network ---
listening-ip=87.106.194.178
relay-ip=87.106.194.178
external-ip=87.106.194.178

# --- Ports ---
listening-port=0
tls-listening-port=5349

# Disable non-TLS completely

#do NOT accept non-encrypted TURN traffic. 

no-udp
no-tcp

# --- Auth ---
realm=turn.radioteletype.net
server-name=turn.radioteletype.net

fingerprint
lt-cred-mech

user=rtty:[VERY SECRET PASSWORD]

# --- TLS ---
cert=/etc/letsencrypt/live/turn.radioteletype.net/fullchain.pem
pkey=/etc/letsencrypt/live/turn.radioteletype.net/privkey.pem

# --- Relay Ports ---
min-port=49160
max-port=49200

# --- Logging ---
verbose

This locks TURN to TLS on port 5349 and restricts relay traffic to a small firewall range.

X-FTP file transfer

Chunked transfer.
Browser Blob.

X-FTP uses a dedicated ordered WebRTC DataChannel. The receiver accepts first, then the file is streamed in 32 KB pieces with progress and speed feedback.

Offer Sender shares filename, size, and MIME type. Receiver can accept, reject, or cancel.

→

Chunks The file is sliced into 32 KB chunks and sent in order.

32 KB 32 KB 32 KB 32 KB

→

Blob URL Received chunks stay in browser memory, then become a Blob/object URL for open or download.

Not permanent storage Files are not saved to a server. Object URLs are revoked when removed or when the page unloads.

Runtime error . . . Runtime error . . . Runtime error

MISSION ACCOMPLISHED!

The project will be made open source after the exam, and will remain that way.

Thank you for your attention!

Browser Radiofor private communication

Fast communication.Minimal identity.

WebSockets introduces peers.WebRTCcarries data.

The backend assigns roles.The frontend starts WebRTC.