Test network connectivity and latency using ping command.
Check if a port is open using telnet or netcat.
Flush DNS cache on Windows, macOS, and Linux when old DNS records are causing websites or services to resolve incorrectly.
Check DNS resolution with nslookup and dig so you can see which IP address a domain is actually resolving to.
Trace the network route with tracert or traceroute so you can see where a connection is slowing down or failing.
Check listening ports on your system so you can confirm whether a service is actually waiting for connections.
Find IP address conflicts on a local network using nbtstat command.
Refresh IP and DNS settings in Windows using ipconfig commands.