test.erl

-module(tcp_to_mqtt).
-behaviour(ranch_protocol).

-export([start_link/4]).
-export([init/3]).

-include_lib("kernel/include/logger.hrl").

start_link(Ref, _Socket, Transport, Opts) ->
    Pid = spawn_link(?MODULE, init, [Ref, Transport, Opts]),
    {ok, Pid}.

init(Ref, Transport, _Opts = []) ->
    {ok, Socket} = ranch:handshake(Ref),
    loop(Socket, Transport).

loop(Socket, Transport) ->
    case Transport:recv(Socket, 0, infinity) of
	{ok, Data} when Data =/= <<4>> ->
             io:format("~p~n", [Data]),
             Json = jiffy(Data),
             send_mqtt(Type, IMEI, Json),
	     loop(Socket, Transport);
	_ ->
	          ok = Transport:close(Socket)
    end.

send_mqtt(Type, Data, Json) ->
    {ok, ConnPid} = emqtt:start_link([{clientid, <<"t2m">>}]),
    {ok, _Props} = emqtt:connect(ConnPid),
    case Type of 
        <<"ALERT">> ->
            ok = emqtt:publish(ConnPid, <<"topic">>, #{}, Json, [{qos, 0}, {retain, true}]);
        _ ->
            ok
    end,
    ok = emqtt:publish(ConnPid, <<"topic2">>, #{}, Json, [{qos, 0}, {retain, true}]),
    ok = emqtt:disconnect(ConnPid),
    ok = emqtt:stop(ConnPid).