I have an app with divided code (client / server). On the client side, I'd like socket io to attempt multiple URLs (one at a time) until it connects successfully.
Here's my code:
const BAD_HOST = "http://localhost:8081";
const LOCAL_HOST = "http://localhost:8080";
const SOCKET_CONFIG = {
upgrade: false,
transports: ["websocket"],
auth: { ... }, // Trimmed for brevity
extraHeaders: { ... }, // Trimmed for brevity
};
let socket = io(BAD_HOST, SOCKET_CONFIG); // This connects fine when I use LOCAL_HOST
socket.on("connect_error", (err) => {
console.log(err);
socket = io(LOCAL_HOST, SOCKET_CONFIG); // DOES NOT WORK
});
socket.on("connect", () => { ... } // Trimmed for brevity
In short, when I try to reassign the value for socket to a new io connection, it seems to retain the old, failed connection. My browser continues to throw 'connect_error' messages from the bad url:
WebSocket connection to 'ws://localhost:8081/socket.io/?EIO=4&transport=websocket' failed:
I checked but couldn't find any official documentation on this question.
I think an approach is already discussed here: https://stackoverflow.com/a/22722710/656708
Essentially you have an array of URLs, which in your case would be:
const socketServerURLs = ["http://localhost:8081","http://localhost:8080"];
and then iterate over them, trying to initiate a socket connection, like this:
// something along these lines
socketServerURLs.forEach((url) => {
// ...
socket.connect(url, socketConfiguration, (client) => {});
// ...
}
Then again, I don't know what a BAD_HOST entails. Assuming that you mean that a connection to that host failed, how would you know that without actually trying to connect to it?