After combing through the commits in the socket transport refactor in Phoenix 1.4 much more carefully, I believe I have solved my problem – I thought i would document it here in case anyone else comes across this same issue.
With the new socket transport, sockets do not appear to need their own dispatch transports; Phoenix.Endpoint.Cowboy2Handlers takes care of everything. So I was able to replace the above config with simply:
http: [
dispatch: [
{:_, [
{:_, Phoenix.Endpoint.Cowboy2Handler, {SiteWeb.Endpoint, []}}
]}
]
]


















