Cannot connect to secure wss:// websocket on iOS 11 & earlier

[nickdowell]

The FoundationTransport (used on iOS 11 & earlier) does not establish a secure connection to the host, resulting in a failed connection to hosts that require security.

The following code snippet replicates the problem on all platforms by forcing use of the FoundationTransport

import Starscream

class WebsocketTester: WebSocketDelegate {
    
    var webSocket: WebSocket?
    
    func start() {
        let url = URL(string: "wss://echo.websocket.org")!
        webSocket = WebSocket(request: URLRequest(url: url), engine:
            WSEngine(transport: FoundationTransport(), certPinner: FoundationSecurity()))
        webSocket?.delegate = self
        webSocket?.connect()
    }
    
    func didReceive(event: WebSocketEvent, client: WebSocket) {
        print(#function, event)
    }
}

The output of running this is

didReceive(event:client:) cancelled

This has previously been reported in #728

[jaltreuter]

@nickdowell thank you for putting up that pull request. This same issue started happening in my app after upgrading from Starscream 3.0.5 to 4.0.0. I ended up simply making a copy of FoundationTransport and adding your changes, and that was effective at solving the problem.

I'd love to see this get some attention from the devs, since it's easily reproducible and affects a reasonably large audience.