Getting remote-schema-error when adding remote schema of a localhost url

[rnjailamba]

Hi, we are getting the below remote-schema-error only with a localhost url on Hasura development enviroment.
We used hasura init, hasura console to scaffold initial structure of the project and have our remote server configured on config.yml as endpoint. We have tried other alternatives anyways such as http://localhost:3000/dev/graphql http://127.0.0.1:3000/dev/graphql http://host.docker.internal/dev/graphql and all have failed in similar way -

{
    "internal": {
        "message": "ConnectionFailure Network.Socket.connect: <socket: 27>: does not exist (Connection refused)",
        "request": {
            "proxy": null,
            "secure": false,
            "path": "/dev/graphql",
            "responseTimeout": "ResponseTimeoutMicro 60000000",
            "method": "POST",
            "host": "127.0.0.1",
            "requestVersion": "HTTP/1.1",
            "redirectCount": "10",
            "port": "3000"
        }
    },
    "path": "$.args[1].args",
    "error": "HTTP exception occurred while sending the request to http://127.0.0.1:3000/dev/graphql",
    "code": "remote-schema-error"
}

[rnjailamba]

Quoting @praveenweb 's answer on a discord chat -

The localhost URL for your remote schema won't work. If Hasura is running on cloud, it doesn't know what host.docker.internal means from that cloud server. It needs a publicly accessible http endpoint.
You have 2 options: 1) Run Hasura locally and do local dev of both Hasura and remote schema. 2) If Hasura is on Cloud, then your remote schema needs to be on some cloud server too. Workaround is to use tool like ngrok.io to expose your local endpoint on a http endpoint that can be added to Hasura Cloud as a remote schema.