A service name resolves correctly but connections time out. How would you investigate?

Confirm the resolved address and port, then test reachability from the affected client environment. Inspect routing, security groups or firewall rules, service binding, load-balancer health, and whether the server is listening. A successful DNS lookup establishes name resolution, not that a transport connection can be made. Separate connection timeout from TLS handshake timeout and application response timeout using traces and logs. Compare working and failing clients and check IPv4 versus IPv6 behavior. Do not rely on ping alone because ICMP and application traffic may follow different policies.