Make it possible to configure each listener's interface IP

src/mtproto_proxy.app.src

@@ -30,10 +30,15 @@
         %% {external_ip, "YOUR.SERVER.EXTERNAL.IP"},
 
         %% Interface to listen for incoming connections
-        {ip, {0, 0, 0, 0}},
+        %% If not set, 0.0.0.0 will be used
+        {listen_ip, {0, 0, 0, 0}},
         %% You can add as much as you want. Names and ports should be unique
         {ports, [#{name => mtp_handler,
                    port => 1443,
+                   %% You can tell it to listen on specific IP.
+                   %% If not set, top-level listen_ip will be used.
+                   %% listen_ip => {1, 2, 3, 4},
+
                    %% secret should be 32 hex chars [0-9a-f]
                    secret => <<"d0d6e111bada5511fcce9584deadbeef">>,
                    %% tag is what you get from @MTProxybot

src/mtproto_proxy_app.erl

@@ -8,7 +8,7 @@
 -behaviour(application).
 
 %% Application callbacks
--export([start/2, stop/1]).
+-export([start/2, stop/1, start_proxy/1]).
 -define(APP, mtproto_proxy).
 
 %%====================================================================
@@ -30,8 +30,10 @@ stop(_State) ->
 %%====================================================================
 %% Internal functions
 %%====================================================================
-start_proxy(#{name := Name, port := Port, secret := Secret, tag := Tag}) ->
-    ListenIp = application:get_env(?APP, ip, {0, 0, 0, 0}),
+start_proxy(#{name := Name, port := Port, secret := Secret, tag := Tag} = P) ->
+    ListenIp = maps:get(
+                 listen_ip, P,
+                 application:get_env(?APP, listen_ip, {0, 0, 0, 0})),
     NumAcceptors = application:get_env(?APP, num_acceptors, 60),
     MaxConnections = application:get_env(?APP, max_connections, 10240),
     Res =