Test if a Network Port is Open
When an application cannot connect, I usually test the port before changing firewall rules or blaming DNS. A quick TCP test tells me whether the client can reach the service at all. These are the Windows tools I use most often: Test-NetConnection, a small .NET TcpClient check, Telnet, and PortQry. Quick answer To test whether a TCP port is open from Windows, run Test-NetConnection -ComputerName servername -Port 443 and check TcpTestSucceeded. True means the client reached the service on that port. False means the port is closed, blocked by a firewall, the service is not listening, or the network path is unavailable. On older systems, use Telnet, PortQry, or a .NET TcpClient test. ...