Example source file for pinging EC2 UDp server http://wp.me/p2fInN-tA

YourGameInstance.cpp

void UYourGameInstance::CheckIfServerIsOnline(FString ServerIP, FString ServerPort)
{
	/* First bind our OnServerCheckFinished function to PingResult.
	* When we get any reply from UDP server PingResult will be called
	* and when PingResult is called the binded method (OnServerCheckFinished) is also called. */
	PingReult.BindUObject(this, &UYourGameInstance::OnServerCheckFinished);

	/* Our UDP server ip (public ip) and port we have to ping.
	* Port should be the exact same port we defined on UDP server node.js file on EC2 server */
	const FString Address = FString::Printf(TEXT("%s:%d"), *ServerIP, ServerPort);

	// Finally just ping.
	FUDPPing::UDPEcho(Address, 5.f, PingReult);
}

void UYourGameInstance::OnServerCheckFinished(FIcmpEchoResult Result)
{
	// Unbind the function. Its no longer required.
	PingReult.Unbind();

	// Simply set a status.
	FString PingStatus = "Ping Failed";

	// Do your stuff based on the result.
	switch (Result.Status)
	{
		case EIcmpResponseStatus::Success:
			PingStatus = "Success";
			break;
		case EIcmpResponseStatus::Timeout:
			PingStatus = "Timeout";
			break;
		case EIcmpResponseStatus::Unreachable:
			PingStatus = "Unreachable";
			break;
		case EIcmpResponseStatus::Unresolvable:
			PingStatus = "Unresolvable";
			break;
		case EIcmpResponseStatus::InternalError:
			PingStatus = "Internal Error";
			break;
		default:
			PingStatus = "Unknown Error";
			break;
	}

	// Simple log
	UE_LOG(LogTemp, Display, "Ping Result is " + PingStatus);
}