Google Cast
Google Cast lets a sender control a receiver that may fetch media directly from a service. Mirroring and direct playback have different network paths; standard Cast and managed cast moderator are separate profiles.
Scope: Google Cast — requirements depend on the selected profile.
protocol · Catalog reviewed 2026-10-21
Related requirements
Review these entries for the services used in your design.
By Google
Infrastructure Requirements
- Compatible sender and receiver applications
- discovery or managed moderator setup
- receiver access to selected content and authentication services.
Network & Physical Requirements
| Port / allocation | Transport | Connection / signal flow | Feature and requirement | Evidence |
|---|---|---|---|---|
| 8009 (default) | TCP | Cast sender → Cast receiver | Profile requirement · Core Cast receiver control Chromium Cast control implementation Default Cast receiver control port; discovery may advertise an endpoint port. | Source checked 2026-09-27 kCastControlPort constant |
| 8008–8009 | TCP | Managed sender → Managed receiver | Optional · Cast moderator Managed cast moderator session setup Chrome Education cast moderator only This managed mode does not rely on ordinary Cast mDNS. Follow its separate UDP/media and cloud requirements. | Source checked 2026-09-27 Cast receiver requirements > inbound traffic |
| Negotiated | UDP | Managed sender / receiver → Managed receiver / sender | Optional · Managed cast moderator Managed cast moderator mirroring media Chrome Education cast moderator only Google specifies UDP 1–65535 in both directions between sender and receiver; resolve the managed casting design before approving this broad allowance. | Source checked 2026-09-27 Cast receiver requirements > inbound and outbound traffic |
| 443 | TCP | Managed sender and receiver → castedumessaging-pa.googleapis.com | Optional · Managed cast moderator Managed cast moderator messaging service Chrome Education cast moderator only HTTPS to the documented messaging service; assess any selected external content services separately. | Source checked 2026-09-27 Receiver and sender requirements |
| 5353 | UDP Multicast: 224.0.0.251 | Local discovery participant → Local discovery peers | Optional · mDNS discovery Local mDNS discovery Standard local Cast; not required for managed cast moderator Queries and responses in both directions; design any cross-subnet discovery gateway explicitly. | Source checked 2026-09-27 Discovery of Cast receivers |
| 1900 (default) | UDP Multicast: 239.255.255.250 | DIAL sender → DIAL-capable receiver | Optional · DIAL discovery Legacy DIAL / SSDP receiver discovery Chromium DIAL discovery; only receivers/apps that enable this service Optional DIAL/SSDP discovery. Enable only for receiver and application combinations that use this service; receiver control and media transport are separate requirements. | Source checked 2026-10-21 kDialRequestAddress and kDialRequestPort constants |
| Negotiated | UDP | Cast sender → Cast receiver | Optional · mirroring Standard Cast screen / tab mirroring media Cast Streaming screen/tab mirroring using the Open Screen OFFER/ANSWER session protocol; confirm selected receiver implementation The receiver returns a UDP media port in the session ANSWER; the protocol uses that port for session RTP and RTCP streams. No universal fixed port range is asserted. Capture the negotiated allocation and validate the selected receiver/firmware before approving a bounded firewall schedule. Managed cast moderator has its own separately scoped network profile. | Source checked 2026-10-21 Answer Object Definition — udpPort; streaming negotiation and active media flow |
Physical, link and configuration requirements
configuration · Profile requirement · Core
Separate sender-to-receiver control from receiver application and content access.
Google Cast application planning
Inventory the selected receiver app, media origin and any license/authentication services. Screen mirroring has a separate sender-to-receiver media path.
Source checked 2026-09-27
Sender and Receiver architecture; receiver types
Gotchas & IT Notes
- ⚠Normal Cast discovers googlecast.tcp through mDNS. Cast moderator differs; do not mix the managed profile into every Chromecast rule.
- ⚠Validate receiver-to-content/CDN access as well as sender-to-receiver control and negotiated media.