iex -S mix while phoenix.server is running

out.sh

➜  trophus git:(master) ✗ iex -S mix
Erlang/OTP 18 [erts-7.0] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Compiled lib/trophus/session.ex
Compiled web/controllers/conversation_controller.ex
Generated trophus app
[error] Running Trophus.Endpoint with Cowboy on http://localhost:4000 failed, port already in use

=INFO REPORT==== 19-Jul-2015::21:37:01 ===
    application: logger
    exited: stopped
    type: temporary

=INFO REPORT==== 19-Jul-2015::21:37:01 ===
    application: hackney
    exited: stopped
    type: temporary

=INFO REPORT==== 19-Jul-2015::21:37:01 ===
    application: idna
    exited: stopped
    type: temporary
** (Mix) Could not start application trophus: Trophus.start(:normal, []) returned an error: shutdown: failed to start child: Trophus.Endpoint
    ** (EXIT) shutdown: failed to start child: Phoenix.Endpoint.Server
        ** (EXIT) shutdown: failed to start child: {:ranch_listener_sup, Trophus.Endpoint.HTTP}
            ** (EXIT) shutdown: failed to start child: :ranch_acceptors_sup
                ** (EXIT) an exception was raised:
                    ** (MatchError) no match of right hand side value: {:error, :eaddrinuse}
                        (ranch) src/ranch_acceptors_sup.erl:30: :ranch_acceptors_sup.init/1
                        (stdlib) supervisor.erl:272: :supervisor.init/1
                        (stdlib) gen_server.erl:328: :gen_server.init_it/6