Ionic - iOS - FTP transfer

Ionic Framework ionic-v3
1

Working on Ionic app, I’ve got a problem with FTP transfer on iOS. It works on Android.
Using ionic-native FTP plugin. Connection succeed, but in about 20 seconds I get the connection timeout error.

    [Log] Login successful – "Init connect and login OK. (iOS always succeed)" (cordova.js, line 1731)
    [Error] Stream timed out with no response from server.
    	(anonymous function) (cordova.js:1731)
    	(anonymous function) (main.js:3835)
    	__tryOrUnsub (vendor.js:23021)
    	error (vendor.js:22980)
    	_error (vendor.js:22911)
    	error (vendor.js:22885)
    	(anonymous function)
    	callbackFromNative (cordova.js:293)
    	(anonymous function) (ios-wkwebview-exec.js:129)
    	runTask (polyfills.js:3:10845)
    	invokeTask (polyfills.js:3:16802)
    	n (polyfills.js:3)

Any ideas how to solve it? Thanks in advance.