what port does the socketIO client listen to by default?
It listens on the port the server listens to. Imagine you set your server to listen port 8080. Then you load your page at http://localhost:8080 and the server returns the page which contains the socket related JS code.
- If you don't specify any port or host as in
var socket = io.connect();, it defaults to the host and port of the current page. - If you specify only the host which is same as the current host, it defaults to the port of the current host.
- If you specify only the host which is different from the current host, it defaults to port
80if the protocol is HTTP. If the protocol is HTTPS, then the port defaults to443.
Here is the related code for url.js parser.