Networking / RFC

Use Get-NetTCPConnection to passively observe ESTABLISHED and TIME_WAIT states, bridging RFC 9293 TCP state transitions to practical troubleshooting.

Establish a TLS connection from PowerShell using TcpClient and SslStream, and read-only check the Subject, NotAfter, and remaining days of the presented certificate.

Send and receive data on localhost using UdpClient in PowerShell to observe datagram communication, which unlike TCP does not require establishing a connection.

Perform initial triage of SSO flows, shortened URLs, and legacy internal link forwarding paths by observing 3xx status codes and Location headers with curl.

We test a length prefix, which adds a 4-byte length to the TCP byte stream so the receiving side can determine message boundaries.

Safely observe how the number of sends and the boundaries of receives do not match in TCP transmission and reception on localhost.

Use curl options such as -I, -L, and url_effective to isolate and verify 301/302 Location headers, intermediate paths, and final URLs.

Set up a TCP server and client on a single PC using the IPv6 loopback ::1, and observe the differences in endpoints and AddressFamilies.

Review the HTTP meanings of 404, 502, and 504 based on RFC 9110, and organize where to start investigating across Nginx and upstream applications along the request path.

Use .NET TcpClient and SslStream from PowerShell to check the server certificate, expiration date, and remaining days of an HTTPS site.