Port 3478 (UDP) — STUN/TURN server (WebRTC)

Enterno.io Editorial Team

Port 3478: STUN/TURN server (WebRTC)

By Anatoly Oshmanovsky · Updated Apr 17, 2026

Key idea:

Port 3478 (UDP) is the standard for STUN/TURN server (WebRTC). STUN (Session Traversal Utilities for NAT) and TURN — NAT-traversal protocols for WebRTC. Port 3478 — UDP and TCP. WebRTC clients use it to discover external IP + traverse fire

Below: what uses this port, security considerations, online check, FAQ.

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What is on this port

STUN/TURN server (WebRTC)

STUN (Session Traversal Utilities for NAT) and TURN — NAT-traversal protocols for WebRTC. Port 3478 — UDP and TCP. WebRTC clients use it to discover external IP + traverse firewalls. Popular servers: coturn (open source), Twilio STUN/TURN (SaaS).

Security considerations

TURN server without auth = relay for arbitrary traffic. Requires TURN secret. STUN is safe (just returns external IP).

Check this port online

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Ping sends ICMP packets to a host and measures response time. Port scanning checks which TCP ports are open and accepting connections — helping diagnose serviceavailability issues.

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Choose packet count (3, 4, 6, 10). Stats: min/avg/max latency and packet loss.

Common Port Scanner

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Testing from our server — see site availability from outside, not just your local network.

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Who uses this

DevOps

availability diagnosis

Network engineers

TCP port scanning

Developers

connection debugging

SRE

basic health check

Common Mistakes

❌

ICMP blocked = server is downMany servers block ICMP. Ping fails but site works — check ports instead.

❌

High ping = server problemLatency depends on geography. 150ms between continents is normal, not an error.

❌

Closed ports — cause for alarmClosed ports of unused services are good. Unnecessary open ports are a risk.

❌

One check = sufficientNetworks are unstable. A single timeout ≠ a problem. Check multiple times or set up monitoring.

Best Practices

✓

Combine ping and port checksPing shows host availability, ports show specific service availability. Use both.

✓

Check from different locationsThe problem may be local. A cloud test shows the real picture.

✓

Close unused portsEvery open port is a potential attack vector. Keep only necessary ports open.

✓

Set up monitoringManual checks do not scale. Set up automated monitoring with notifications.

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Research

Open Port Exposure in Runet 2026

Alternatives

Frequently Asked Questions

Is port 3478 open by default?

No, modern cloud providers (AWS, Google Cloud, Yandex) close all incoming ports by default. You must explicitly allow port 3478 in a Security Group or firewall.

How to check if my port 3478 is reachable?

Use <a href="/en/ping">Enterno Ping + Port Checker</a>. Or in shell: <code>nc -vz example.com 3478</code> or <code>telnet example.com 3478</code>.

Is port 3478 safe to expose?

Depends on the service. STUN/TURN server (WebRTC) should never be exposed publicly without authentication + TLS. See <a href="/en/s/research-open-ports-exposure-2026">our 2026 exposure research</a>.