Windows 10: ESP8266 hostByName fails on specific IPAddress

I'm using ESP8266's to create time controlled switches and I can't get an IPAddress to work with WiFi.hostByName().When the ESP units try to get an ntp Server address, all IPAddresses I try work except 192.168.1.243 which fails with "(IP unset)" and shows no network activity.

The problem seems to occur when Wifi.config(), WiFi.hostByName() and possibly WiFi.hostname() are used together.Any ideas about why this one address doesn't work?

Notes:

Using win10-1903-18362

Ideas tried that didn't work:
1. Flush the DNS cache.
2. Restart the router.
3. Clean out the hosts file.
4. Check the other devices an see that they don't use the address.
5. Verify there's no reference to the address in the registry.
6. Use a utility to search the network to see if the address is already online elsewhere.

This is the simplified code:
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
#include <stdio.h>
#include <string.h>

IPAddress hostIP = IPAddress(192, 168, 1, 243);
IPAddress gateway = IPAddress(192, 168, 1, 1);
IPAddress subnet = IPAddress(255, 255, 255, 0));

void setup()
{
Serial.begin(115200);
while(!Serial);
WiFiUDP Udp;
WiFiServer server(80);

Serial.print("\nConnecting to ");
Serial.println(ssid);
WiFi.hostname("ESP8266_243");
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED)
{
delay(500);
Serial.print(".");
}
Serial.println("\nWiFi connected.");

WiFi.config(hostIP, gateway, subnet);
Udp.begin(4333);
IPAddress ntpServerIP;
WiFi.hostByName("us.pool.ntp.org", ntpServerIP);
} //Setup

void Loop()
{
}

:)

 

How to add a bypass ipaddress in firewall

I'm getting a connection failure to one of my server from my local win 10 laptop and i want to rule out if its the firewall that is stopping it do so. So want to bypass just that ipaddress of my server in the firewall at my local laptop. Can someone please
help on what can be the steps to do that?

Thanks,

 

Windows 10 fails to update


When you finish testing the Avast suggestion, make sure that you restart your machine.

Then if the issue persists, please return to the trouble shooting list in post# 89

I think there are three steps that remain; the WU troubleshooter, reset WU components, and manual WU reset.

 

KB4025339 Fails Install 0x80070564


Thanks
I am trying Eagle 51's suggestions now. Windows Update troubleshooter found a bunch of errors and fixed all but one.The update is trying to download KB4025339 again. I'll see what happens. At step one troubleshooter finishes with one error unresolved "Potential Windows Update Database Error Detected-Not Fixed". Windows update stalled at 0%.

At step 2 same troubleshooter error. The KB finished a new download failed to install.
Did step 3 KB has downloaded but fails to install.

If Eagle's suggestion doesn't work I'll try EdTittel's suggestion

Tried bothe Eagle & Ed 's suggestions - do not work. Anyone else?

I have noticed that the latest update for my nvidia drivers has failed to update. Wondering about that!