Documentation Index

Fetch the complete documentation index at: https://developers.telnyx.com/llms.txt

Use this file to discover all available pages before exploring further.

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Network Connectivity Requirements

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Overview

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Signaling

• Outbound WebSocket connections must be allowed on port 443
• No HTTP long-polling fallback — WebSocket is required
• Connection must remain open for the duration of the session

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STUN

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TURN

• UDP (preferred) — Lower latency, better for real-time audio
• TCP (fallback) — Higher latency, used only when UDP is blocked

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Firewall Configuration

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Minimum required rules

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Optional but recommended

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Media ports

• Ensure TURN is accessible — TURN handles media relay when direct connectivity fails
• Allow UDP outbound to Telnyx media servers (the remote_media_ip seen in SDP)
• Don’t restrict outbound UDP to specific ports — this will break WebRTC

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Restrictive Network Scenarios

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STUN fails (error 701)

1. Check firewall allows UDP to stun.telnyx.com:3478
2. If STUN is blocked, TURN may still work — the SDK falls back automatically
3. If both STUN and TURN are blocked, calls cannot connect

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TURN fails

1. Check firewall allows TCP/443 to turn.telnyx.com
2. If UDP is blocked, TCP TURN will work but with higher latency
3. As a last resort, use forceRelayCandidate: true to skip direct connectivity attempts:

const call = client.newCall({
 destinationNumber: '+12345678900',
 forceRelayCandidate: true,
});

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Corporate VPN

1. Whitelist rtc.telnyx.com, stun.telnyx.com, and turn.telnyx.com in VPN split-tunneling config
2. Ensure VPN doesn’t block UDP traffic to TURN servers
3. Consider split-tunneling so WebRTC traffic bypasses the VPN

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Docker / Container environments

1. Docker’s default bridge network (172.x or 10.x) can interfere with ICE candidate gathering
2. Use --network host mode for the container
3. Or configure the Docker network to use the host’s network stack

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Testing Connectivity

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Quick test

// Test WebSocket signaling
const ws = new WebSocket('wss://rtc.telnyx.com:443');
ws.onopen = () => console.log(' WebSocket OK');
ws.onerror = () => console.error(' WebSocket FAILED');

// Test STUN
const pc = new RTCPeerConnection({
 iceServers: [{ urls: 'stun:stun.telnyx.com:3478' }],
});
pc.createDataChannel('test');
pc.createOffer().then(offer => pc.setLocalDescription(offer));
pc.onicecandidate = (e) => {
 if (e.candidate) {
 const type = e.candidate.type;
 console.log(`ICE candidate type: ${type}`);
 if (type === 'srflx') console.log(' STUN works');
 if (type === 'relay') console.log(' TURN works');
 }
};

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Debug tools

• SDK debug mode: Set debug: true and debugOutput: 'socket' in IClientOptions
• Debug visualizer: Upload debug data to https://webrtc-debug.telnyx.com/
• Call reports: Enable enableCallReports: true for programmatic access to ICE stats

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Bandwidth Requirements

• Audio only: 100 kbps (including overhead)
• With video: 500-2000 kbps depending on resolution

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See Also

• IClientOptions — ICE and network configuration
• Debug Data & Call Quality Analysis — Interpreting ICE and quality data
• Best Practices — Production deployment guide
• Error Handling — ICE and WebSocket error codes