Is the destination hostname or IP address specified correct?
Specify the correct port number.
Are the network cables connected correctly?
Is the WiFi connection working?
Is the RJ45 jack seated correctly and the clip not broken?
Is network environment/equipment operating correctly?
Network switch
Network switch ports
Source and Destination network ports
Home/Business Internet Router
The internet router could blocking the traffic in it security settings
Is the IP address for the GATEWAY set to the correct value