What does HRESULT 0xC00D11B6 (NS_E_WMP_NETWORK_FIREWALL) mean?

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Description:

Windows Media Player cannot play the file. A network firewall might be preventing the Player from opening the file by using the UDP transport protocol. If you typed a URL in the Open URL dialog box, try using a different transport protocol (for example, "http:").%0

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NS_E_WMP_DRM_LICENSE_SERVER_UNAVAILABLE	NS_E_WMP_NO_REMOVABLE_MEDIA

NS_E_WMP_NETWORK_FIREWALL

Diagnosing NS_E_WMP_NETWORK_FIREWALL in the Windows Media Player playback path

NS_E_WMP_NETWORK_FIREWALL (0xC00D11B6) is returned when the selected streaming transport, commonly UDP in the legacy Player path, appears blocked by a firewall or NAT policy.

Compare the same media resource over the selected streaming transport and a supported TCP or HTTP fallback. That isolates firewall or NAT handling without changing the content or decoder path.

Controlled playback comparison

Capture the resource identity and protocol rollover, local UDP ports, outbound and inbound rules, packet capture, NAT mapping and HTTP fallback result.
Verify that the caller uses the current Playlist, Media, Network, graph, device or DRM object instance.
Run the narrow experiment: force an HTTP/TCP-supported URL path and compare it with the UDP attempt using the same media resource.
Do not combine this focused test with a codec-pack change, Player reset, or broad registry cleanup.
If the retest returns a different specific HRESULT, diagnose that new failure as the next stage.

Actions that obscure the cause

opening unrelated inbound ports.

Technical references

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