'.createServer' is undefined in browser

[mkg20001]

The .createServer function should exist in the browser and return an error in the callback if called instead of simply being undefined

[dryajov]

I'm guessing that the listener should not be loaded in browsers at all, take a look at the websocket transport and how its loaded in libp2p - the dialer part is always loaded, but the listener doesn't get instantiated in the browser.

[mkg20001]

I was talking about replacing it with a function in the browser like function createServer() { throw new Error('WebSockets servers can\'t be created in the browser'); } instead of replacing the function with undefined and causing confusing error messages to appear in the browser.