Realtime Database viewer making requests to 0.0.0.0 and not displaying contents of Realtime Database.

[REQUIRED] Environment info

**firebase-tools: 13.3.0

Platform: Linux Docker Container

[REQUIRED] Test case

Create a docker container with the following Dockerfile

FROM node:18-alpine

RUN apk add openjdk11

# Install firebase tools.
RUN npm install -g firebase-tools@13.3.0

RUN firebase setup:emulators:ui

WORKDIR /firebase
CMD firebase --project someProjectId  emulators:start --import=/firebase/fixtures --export-on-exit

Use the following firebase.json file

{
  "emulators": {
    "singleProjectMode": false,
    "firestore": {
      "port": 5000,
      "host": "0.0.0.0",
      "indexes": "firestore-indexes.json"
    },
    "auth": {
      "port": "5001",
      "host": "0.0.0.0"
    },
    "database": {
      "port": "5002",
      "host": "0.0.0.0"
    },
    "hub": {
      "host": "0.0.0.0"
    },
    "logging": {
      "host": "0.0.0.0"
    },
    "ui": {
      "enabled": true,
      "host": "0.0.0.0",
      "port": 4000
    }
  }
}

Run container using the following command

docker run --rm -v /home/dev/firebase:[Location to above firebase config] -d -it --name firebase  -p 9150:9150 -p 5000-5002:5000-5002 -p 4000:4000 -p 4500:4500 firebase:v11

[REQUIRED] Steps to reproduce

Access the above docker container firebase emulator UIfrom another machine through a local network

[REQUIRED] Expected behavior

The Realtime DB viewer should show the content of the Database

[REQUIRED] Actual behavior

The browser makes requests to 0.0.0.0 due to some config error in the firebase tooling and the realtime database page does not display the contents

Below is the umatrix extension showing the requests to 0.0.0.0

Below is the network requests from the browser dev tools window.

Below is the realtime database page showing tables but no content

A couple of additional notes to help with the issue

I run the emulator in a docker container on a mac studio. The VM is running in bridge mode and the container obtains an IP within the local network
I access the emulators from my laptop (separate machine)
This setup use to work with an older version of Firebase tools (v11) where all running emulators would display their data correctly. I recently decided to upgrade to the latest version.
I also use pihole on my network but I believe all DNS records requested by the emulator tools have been whitelisted.
Firestore and Auth emulators work as expected showing the data

Ok so I seem to have solved the issue but not sure why its happening. I have the docker container associated with an internal dns host that is resolved by the Pihole located on the network. This DNS name is not resolvable publicly. If I access the emulator UI using the IP address directly in the browser, the Database Viewer works as expected and displays the data. If I use the hostname for somereason the Database viewer page starts requesting 0.0.0.0 again. Not sure why this is happening. If I shell into the docker container and use nslookup, the hostname resolves to the Linux VM running the container.

Does the emulator use its own DNS resolver and ignore the hosts dns settings by any chance?

As a side note, I am also seeing similaer behaviour ion the flutterfire android client library for the realtime database

D/Connection(  505): conn_2 - Opening a connection
D/WebSocket(  505): ws_2 - WebSocket error.
D/WebSocket(  505): com.google.firebase.database.tubesock.WebSocketException: error while creating socket to ws://0.0.0.0:5002/.ws?ns=canvas-advice-333009-default-rtdb&v=5&ls=up1KgIKErjlxgIgM0EQ2wg4r98LiNTYH
D/WebSocket(  505):     at com.google.firebase.database.tubesock.WebSocket.createSocket(WebSocket.java:301)
D/WebSocket(  505):     at com.google.firebase.database.tubesock.WebSocket.runReader(WebSocket.java:360)
D/WebSocket(  505):     at com.google.firebase.database.tubesock.WebSocket.access$000(WebSocket.java:47)
D/WebSocket(  505):     at com.google.firebase.database.tubesock.WebSocket$2.run(WebSocket.java:143)
D/WebSocket(  505):     at java.lang.Thread.run(Thread.java:764)
D/WebSocket(  505): Caused by: java.net.ConnectException: failed to connect to localhost/127.0.0.1 (port 5002) from /:: (port 35356): connect failed: ECONNREFUSED (Connection refused)
D/WebSocket(  505):     at libcore.io.IoBridge.connect(IoBridge.java:138)
D/WebSocket(  505):     at java.net.PlainSocketImpl.socketConnect(PlainSocketImpl.java:129)
D/WebSocket(  505):     at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:356)
D/WebSocket(  505):     at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:198)
D/WebSocket(  505):     at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
D/WebSocket(  505):     at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356)
D/WebSocket(  505):     at java.net.Socket.connect(Socket.java:616)
D/WebSocket(  505):     at java.net.Socket.connect(Socket.java:565)
D/WebSocket(  505):     at java.net.Socket.<init>(Socket.java:445)
D/WebSocket(  505):     at java.net.Socket.<init>(Socket.java:217)
D/WebSocket(  505):     at com.google.firebase.database.tubesock.WebSocket.createSocket(WebSocket.java:297)
D/WebSocket(  505):     ... 4 more
D/WebSocket(  505): Caused by: android.system.ErrnoException: connect failed: ECONNREFUSED (Connection refused)
D/WebSocket(  505):     at libcore.io.Linux.connect(Native Method)
D/WebSocket(  505):     at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:126)
D/WebSocket(  505):     at libcore.io.IoBridge.connectErrno(IoBridge.java:152)
D/WebSocket(  505):     at libcore.io.IoBridge.connect(IoBridge.java:130)
D/WebSocket(  505):     ... 14 more
D/WebSocket(  505): ws_2 - closing itself

Some furthe debugging from the realtime database client running on an Android emulator

D/PersistentConnection( 5482): pc_0 - Trying to fetch auth token
D/PersistentConnection( 5482): pc_0 - Trying to fetch app check token
D/PersistentConnection( 5482): pc_0 - Successfully fetched token, opening connection
D/Connection( 5482): conn_0 - Opening a connection
D/WebSocket( 5482): ws_0 - websocket opened
D/WebSocket( 5482): ws_0 - Reset keepAlive
D/WebSocket( 5482): ws_0 - ws message: {"t":"c","d":{"t":"h","d":{"ts":1708424459584,"v":"5","h":"0.0.0.0:5002","s":"ZofjtuoscNEU0SZf5kjxrKSpW3A3eBlP"}}}
D/WebSocket( 5482): ws_0 - Reset keepAlive. Remaining: 44998
D/WebSocket( 5482): ws_0 - HandleNewFrameCount: 1
D/WebSocket( 5482): ws_0 - handleIncomingFrame complete frame: {t=c, d={t=h, d={h=0.0.0.0:5002, s=ZofjtuoscNEU0SZf5kjxrKSpW3A3eBlP, v=5, ts=1708424459584}}}
D/Connection( 5482): conn_0 - Got control message: {t=h, d={h=0.0.0.0:5002, s=ZofjtuoscNEU0SZf5kjxrKSpW3A3eBlP, v=5, ts=1708424459584}}
D/Connection( 5482): conn_0 - realtime connection established
D/PersistentConnection( 5482): pc_0 - onReady
D/PersistentConnection( 5482): pc_0 - handling timestamp
D/PersistentConnection( 5482): pc_0 - Sending first connection stats

You can see the line output also related 0.0.0.0 D/WebSocket( 5482): ws_0 - ws message: {"t":"c","d":{"t":"h","d":{"ts":1708424459584,"v":"5","h":"0.0.0.0:5002","s":"ZofjtuoscNEU0SZf5kjxrKSpW3A3eBlP"}}}

firebase / firebase-tools