AlexxIT/go2rtc · error

can't open two UDP ports

Error message

can't open two UDP ports

What it means

ListenUDPPair exhausted its retry loop trying to bind two adjacent UDP ports (port and port±1) for RTP/RTCP; at least one bind always failed. Typically caused by firewall restrictions or port exhaustion; no listener pair is returned.

Solutions

1. Free the occupied UDP port range
2. Use TCP interleaved transport instead of UDP

When it happens

Trigger: Thrown at pkg/rtsp/client.go:455 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of AlexxIT/go2rtc@c245815e75 (2026-09-07). Data as JSON: /api/errors/719c887c0f4edc5f. Report an issue: GitHub.

Appendix: source

Thrown at pkg/rtsp/client.go:455

			port2 = port1 - 1
		} else {
			port2 = port1 + 1
		}

		ln2, err := net.ListenUDP("udp", &net.UDPAddr{IP: nil, Port: port2})
		if err != nil {
			_ = ln1.Close()
			continue
		}

		if port1 < port2 {
			return ln1, ln2, nil
		} else {
			return ln2, ln1, nil
		}
	}

	return nil, nil, fmt.Errorf("can't open two UDP ports")
}

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