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For a Home Assistant Container using Docker’s ordinary bridge networking, publish TCP 8123 with 8123:8123. That port serves the web interface, REST API, and WebSocket connection. The official Linux Container example instead uses network_mode: host; in that mode the container uses the host’s network stack, so you must omit ports:.
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HomeKit Bridge and automatic device discovery are separate concerns. HomeKit normally needs UDP 5353 for mDNS and TCP 21063 for the bridge (or whatever bridge port you configured). SSDP, Zeroconf, and similar integrations need multicast or broadcast visibility, which a simple 8123 mapping does not provide. For access from outside your home, use a VPN or Home Assistant Cloud rather than forwarding 8123 directly to the Internet.
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Home Assistant’s ports at a glance
The port you need depends on the networking mode and the integrations you run. Publishing a port makes a container service reachable through the Docker host; it does not automatically make local discovery protocols work.
| Use case | Compose choice | Port or networking requirement | What it does |
|---|---|---|---|
| Web UI, REST API, and WebSocket in bridge mode | Default bridge networking plus ports: |
8123:8123 TCP, or another host port mapped to container port 8123 |
Connects clients on the host or LAN to Home Assistant’s HTTP server. |
| Official Linux Container pattern | network_mode: host |
No ports: section |
The container listens directly on the host network stack. |
| HomeKit Bridge | Bridge mode with multicast support, or host mode | UDP 5353 and TCP 21063 by default; use the integration’s configured bridge port if changed | mDNS advertises the bridge and TCP carries HomeKit traffic. |
| SSDP/UPnP and similar discovery | Usually host mode or a correctly configured multicast relay | No single universal published TCP port | Allows discovery broadcasts and multicast packets to reach Home Assistant. |
| Remote access from outside your home | VPN or Home Assistant Cloud | Do not expose 8123 directly unless you have deliberately designed and secured a reverse-proxy setup | Provides remote connectivity without an unaudited public Home Assistant endpoint. |
How Docker port publishing works
Compose’s short port syntax is [HOST:]CONTAINER[/PROTOCOL]. Therefore, 8123:8123 means “listen on host port 8123 and forward TCP traffic to port 8123 inside the container.” A different host port, such as 8080:8123, still targets Home Assistant’s container port 8123; you would browse to http://host-address:8080.
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If you leave out the host IP, Docker binds the published port to 0.0.0.0, which means every host interface. That can include a Wi-Fi interface, a wired LAN interface, and any other reachable interface on the machine. To restrict exposure, include an address in the mapping and enforce the same policy in the host firewall:
127.0.0.1:8123:8123limits access to programs on the Docker host.192.168.1.20:8123:8123listens only on that host’s LAN address, assuming it is assigned to the machine.0.0.0.0:8123:8123is explicit all-interface binding and should be used only when that is intentional.
Use TCP for the web service. A UDP mapping of 8123 will not provide access to the Home Assistant interface because the server endpoint is TCP-based.
Bridge mode: the normal web-interface setup
Bridge networking gives the container its own network namespace. Docker then needs an explicit host-to-container mapping for clients to reach Home Assistant.
Minimal Compose service
services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
ports:
- "8123:8123"
With that service running, open http://DOCKER_HOST:8123 from a browser on a network that can reach the Docker host. Replace DOCKER_HOST with the host’s DNS name or LAN address; do not use the container’s private bridge address as a permanent client address.
Using another host port
services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
ports:
- "8080:8123"
This changes only the host-side number. Home Assistant still listens on container port 8123, while users connect to port 8080 on the Docker host. Choose a host port that is not already occupied, and document it for bookmarks, reverse proxies, and firewall rules.
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Restricting the listener
services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
ports:
- "192.168.1.20:8123:8123"
The address must exist on the Docker host. If it changes because of DHCP or a network redesign, Docker may fail to start or the service may become unreachable. A static lease or fixed host address avoids that surprise.
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With network_mode: host, the container shares the host’s network stack. Home Assistant binds directly to the host interfaces, which is useful for integrations that depend on LAN multicast, broadcast, or unusual discovery behavior.
services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
network_mode: host
There is deliberately no ports: block. Docker documents host mode as giving the container access to host ports and host traffic; port publishing is unsupported in this mode. Combining the two settings causes Docker Compose to reject the service rather than creating a second mapping.
Host mode also means the container is not isolated from the host’s network namespace. Review which interfaces the host exposes and apply host-firewall rules accordingly. It is a networking choice, not a security feature.
HomeKit Bridge: two different traffic paths
HomeKit Bridge uses mDNS (also called Zeroconf) to advertise itself and a TCP listener for the actual bridge connection. The default requirements are:
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- UDP 5353: mDNS. Home Assistant advertises the
_home-assistant._tcp.local.service and HomeKit discovery relies on this local multicast traffic. - TCP 21063: the default HomeKit Bridge port. If you changed the integration’s
portoption, use that configured value instead of 21063.
A bridge-mode service therefore needs more than the web mapping if you want HomeKit pairing and operation to work through Docker. A conceptual mapping is:
services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
ports:
- "8123:8123"
- "21063:21063/tcp"
- "5353:5353/udp"
Those mappings alone may still be insufficient because Docker’s ordinary bridge does not automatically reproduce the host LAN’s multicast behavior. Home Assistant’s HomeKit guidance recommends host networking when the bridge does not appear in the Home app. If host mode is unsuitable, an mDNS forwarder such as Avahi in reflector mode can relay discovery between the Docker network and the LAN, but it must be configured correctly and allowed through the relevant firewalls.
Pairing problems are therefore not diagnosed by checking only http://host:8123. The web page can work while UDP 5353 is blocked or isolated.
SSDP, UPnP, Zeroconf, and other discovery integrations
Many integrations find devices by listening for local multicast or broadcast packets. SSDP/UPnP is the common example. There is no universal “SSDP port” that you can publish to solve every integration: the important requirement is that discovery packets can travel between the container and the LAN in both directions.
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Use host networking when an integration requires direct LAN visibility and you do not have a reliable multicast design. In a segmented network, a properly configured multicast relay or reflector may work, but the relay must cover the interfaces and groups used by the device protocol. Confirm that switches, Wi-Fi isolation, VLAN ACLs, and host firewalls are not filtering those packets.
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A successful connection to the Home Assistant frontend proves only that TCP web traffic is reachable. It does not prove that SSDP, mDNS, or another discovery protocol can cross the Docker boundary.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Changing Home Assistant’s server port
The server port can be changed in Home Assistant at Settings > System > Network. If you change the listening port, make the Docker mapping and every firewall or proxy rule match the new container-side value.
For example, if Home Assistant is configured to listen on 9000 inside the container, a bridge-mode mapping would target 9000:
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services:
homeassistant:
image: ghcr.io/home-assistant/home-assistant:stable
ports:
- "9000:9000"
If you want users to keep using host port 8123 while the container listens on 9000, map 8123:9000 instead. Do not change the mapping alone and expect the application to follow it; the container service must actually be listening on the target port.
Remote access and reverse proxies
Opening a port on the Docker host is not the same as safely publishing Home Assistant to the Internet. Directly forwarding TCP 8123 from a router exposes the login surface and application endpoint to unsolicited traffic. Home Assistant’s remote-access guidance recommends Home Assistant Cloud or a VPN for this reason.
If you operate a reverse proxy, keep the proxy on the intended public interface, terminate HTTPS there, and configure Home Assistant to trust that proxy correctly. The trusted-proxy configuration must match the proxy’s real source addresses; an overly broad trust rule can let clients forge forwarded addresses. Also keep the internal Home Assistant port off the public router and restrict the host firewall to the proxy or VPN addresses that need it.
Troubleshooting by symptom
The browser cannot open Home Assistant
- Confirm the container is running and inspect its logs for a bind or startup error.
- Run
docker compose psand verify that the expected host-to-container mapping is present. - Check that the host port is not already used by another service.
- Test from the Docker host first, then from a LAN client, to distinguish an application problem from routing or firewall filtering.
- If you used an explicit host IP, verify that address is assigned to the host and that the client is reaching the same interface.
Compose rejects the service configuration
Look for both network_mode: host and ports:. Remove the port mappings when using host mode, or remove host mode and use bridge networking with explicit mappings.
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- Check that the HomeKit Bridge integration is configured and note its selected bridge port.
- Allow UDP 5353 and the configured TCP bridge port through host and network firewalls.
- Check whether the Docker bridge is preventing multicast from reaching the LAN.
- Try host networking, which is the recommended Docker remedy for bridge-discovery problems.
- If host mode is not possible, deploy and test an mDNS reflector on the path between Docker and the HomeKit devices.
Devices are not discovered automatically
Do not add random TCP mappings. Identify the protocol first: SSDP and Zeroconf need multicast or broadcast visibility. Move to host mode or correct the relay, VLAN, Wi-Fi-isolation, and firewall configuration that is blocking those packets.
Deployment checklist
- Choose bridge mode for ordinary web/API access, or host mode when integrations require direct LAN discovery.
- In bridge mode, publish the Home Assistant listening port, normally
8123:8123TCP. - Never combine
network_mode: hostwithports:. - For HomeKit Bridge, account for UDP 5353 and the configured TCP bridge port (21063 by default).
- For SSDP and similar integrations, provide multicast visibility rather than relying on a single published port.
- Remember that an omitted host IP binds to all interfaces; use an explicit address when appropriate.
- Use a VPN or Home Assistant Cloud for remote access instead of direct public forwarding.
- After any server-port change in Settings > System > Network, update Compose, firewalls, proxies, and bookmarks together.
Bottom line
Use 8123:8123 for a bridge-mode Home Assistant Container when you need the web interface and API. Use network_mode: host without any ports: section when host-level LAN visibility is required. HomeKit adds mDNS and a bridge TCP port, while SSDP and other discovery systems depend on multicast behavior rather than an extra 8123 mapping. Keep remote access behind a VPN, Home Assistant Cloud, or a carefully configured reverse proxy.
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