Erlang：与牧场相关的错误的误解

Question

I am trying to make this application FIX protocol

I start the Erlang shell using erl -pa ./ebin -pa ebin ./deps/*/ebin . And run the application like this: application:start(fix) . After that I invoke "start_listener" function like this: fix:start_listener() . As a result this mistake appears:

exception error: no match of right hand side value 
                 {error,
                     {{shutdown,
                          {failed_to_start_child,ranch_acceptors_sup,
                              badarg}},
                      {child,undefined,
                          {ranch_listener_sup,fix_listener},
                          {ranch_listener_sup,start_link,
                              [fix_listener,10,ranch_tcp,
                               [{port,[8501]}],
                               fix_server,[]]},
                          permanent,5000,supervisor,
                          [ranch_listener_sup]}}}
in function  fix:start_listener/0 (src/fix.erl, line 21)

What does it all mean? And how to fix this mistake?

My code is:

`-module(fix).
 -author('Max Lapshin <max@maxidoors.ru>').
 -include("log.hrl").
  % -include("../include/admin.hrl").
 -include("../include/business.hrl").
 -compile(export_all).

  %%  @doc Start acceptor with `ranch' on port, specified in application environment under fix_port%%
  -spec start_listener() -> {ok, pid()}.
   start_listener() ->
   application:start(ranch),
   Spec = ranch:child_spec(fix_listener, 10,
   ranch_tcp, [{port, fix:get_value(fix_port)}],
    fix_server, []
      ),
     {ok, Pid} = supervisor:start_child(fix_sup, Spec),
       error_logger:info_msg("Starting FIX server on port ~p~n",[fix:get_value(fix_port)]),
      {ok, Pid}.

` This is a piece of code that shows a mistake.

Answer 1

This is incorrect:

[{port,[8501]}]

Port value must be an integer. Your fix:get_value function returns list [8501] instead 8501 and you get this badarg error.