# Test single TCP port Test-NetConnection -ComputerName server01 -Port 3389
Portqry was particularly popular for Exchange Server diagnostics, checking ports like 25 (SMTP), 443 (Outlook Anywhere), 587 (SMTP submission), and 993 (IMAP SSL). portqry command
: No process is listening on the port, or a "reset" (ACK-RST) was received. checking ports like 25 (SMTP)
: It can link open ports to the specific Process IDs (PIDs) using them, helping identify which application is responsible for network traffic. 443 (Outlook Anywhere)
portqry -n server01.example.com -o 3389,445,53