mqttClient Service Connect error?

Finally problem resolved: using mosquitto MQTT client and server must to be on the same wlan! I didn’t know it! The problem is that my wifi is 5G and my TaLON wifi card doesn’t read it: so my mangOH was on my phone’s lan and PC on WiFi. So I connected all on my phone’s lan and all work!
Thank you all for the support, especially to @jyijyi . I’m so sorry to have bothered you, but it was a frustrating situation. Thanks again.