preferIPv6Addresses in dev mode

Description of the bug / feature

Starting vaadin 17 in dev mode and with -Djava.net.preferIPv6Addresses=true results in

java.net.ConnectException: Connection refused: no further information
	at java.base/sun.nio.ch.Net.pollConnect(Native Method) ~[na:na]
	at java.base/sun.nio.ch.Net.pollConnectNow(Net.java:660) ~[na:na]
	at java.base/sun.nio.ch.NioSocketImpl.timedFinishConnect(NioSocketImpl.java:549) ~[na:na]
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:597) ~[na:na]
	at java.base/java.net.Socket.connect(Socket.java:648) ~[na:na]
	at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:177) ~[na:na]
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:474) ~[na:na]
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:569) ~[na:na]
	at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:242) ~[na:na]
	at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:341) ~[na:na]
	at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:362) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1261) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1194) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1082) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1016) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1600) ~[na:na]
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1528) ~[na:na]
	at com.vaadin.flow.server.frontend.FrontendUtils.getFileFromWebpack(FrontendUtils.java:602) ~[flow-server-4.0.7.jar:4.0.7]
	at com.vaadin.flow.server.frontend.FrontendUtils.getFileContent(FrontendUtils.java:462) ~[flow-server-4.0.7.jar:4.0.7]

Versions:

- Vaadin / Flow version: 17.0.10
- Java version: 15.0.1.9-hotspot
- OS version: windows 10
- IDE (if applicable): eclipse

[BrunoEberhard]

I use MS SQL Server. In the example how to connect to that DB the flag is listed. I did just copy/paste all the flags and wasn’t aware of the side effects. It works without the flag so no high prio for me. It just was annoying to debug for several hours so I sent you this issues.

[BrunoEberhard]

When the application is running you can reproduce the bug with

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.stream.Collectors;

public class Test {

	public static void main(String[] args) throws Exception {
		URL uri = new URL("http://localhost:57088/VAADIN/index.html");
		
		HttpURLConnection connection = (HttpURLConnection) uri.openConnection();
		connection.setRequestMethod("GET");
		
		try (BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), StandardCharsets.UTF_8))) {
		    String pageText = reader.lines().collect(Collectors.joining("\n"));
		    System.out.println(pageText);
		}
		
	}

}

(of course with adjusted port number)