sync/docs/socketconfig.md

Socket.IO Client Configuration

As of 2015-10-25, the legacy /sioconfig JavaScript for retrieving connection information is being deprecated in favor of a new API. The purpose of this change is to allow partitioning channels across multiple servers in order to better handle increasing traffic.

To get the socket.io configuration for the server hosting a particular channel, make a GET request to /socketconfig/<channel name>.json. The response will be a JSON object containing a list of acceptable servers to connect to, or an error message.

Examples:

GET /socketconfig/test.json
200 OK

{
    "servers": [
        {
            "url": "https://localhost:8443",
            "secure": true
        },
        {
            "url": "http://localhost:1337",
            "secure": false
        },
        {
            "url": "https://local6:8443",
            "secure": true,
            "ipv6": true
        },
        {
            "url": "http://local6:1337",
            "secure": false,
            "ipv6": true
        }
    ]
}

GET /socketconfig/$invalid$.json
404 Not Found

{
    "error": "Channel \"$invalid$\" does not exist."
}

Each entry in the servers array has "secure":true if the connection is secured with TLS, otherwise it it is false. An entry with "ipv6":true indicates that the server is listening on the IPv6 protocol.

You can pick any URL to connect socket.io to in order to join the specified channel. I recommend picking one with "secure":true, only choosing an insecure connection if implementing a TLS connection is infeasible.