Unable to connect to another machine from iOS using RemoteWebDriver

Hello everybody. I'm using AWS Device Farm to run my tests. This is web to mobile testing for video calls, where both desktop pc and mobile phone must be used in one framework. I have a problem to connect to my remote machine in test while using iOS, but everything is fine with Android. I have both Android and iOS applications for mobile testing.
The steps I do to run tests using AWS device farm:

1. We have a remote machine with open static IP address where I have a selenium-server-standalone started;
2. I put my project to AWS Device Farm -> Mobile device testing project -> Create a new project;
3. I fill out all the blanks, upload my application, select Java Appium TestNG, set configuration, create device pool and launch run;
4. Project goes to AWS Device Farm and while method 'setup' is invokes both the remote machine and selected mobile device and tests run;

When I use my Android application, the test is able to connect to my remote machine and then invoke Android phone, then tests run in parallel on both web pc and mobile device.

But when I try to do the same thing with iOS application, I have an unknown problem. I do the same steps with Android. So, the difference is only that it is iOS phone. And when I try to connect to my remote machine, the test skips. Without any log or comment...just skips and that's it.

The way I connect to my machine from AWS Device farm mobile project:

@BeforeTest
public void setUp() {

//web
DesiredCapabilities dc = new DesiredCapabilities();
dc.setBrowserName("chrome");
dc.setPlatform(Platform.ANY);
URL remoteHostURL = new URL("http://x.x.x.x:4444/wd/hub");
DRIVER_WEB.set(new RemoteWebDriver(remoteHostURL, dc));

//mobile
capabilities = CapabilityManager.getAndroidCapabilities();
DRIVER_MOBILE.set(new AppiumDriver<MobileElement>(remoteAppiumHostURL, capabilities));
...
}
What could cause this problem? Cos it works only for Android, but doesn't work for iOS. I'd be very thankful to get any help from you!