This article explains what a 502 Bad Gateway response means, how Nginx as a reverse‑proxy generates it, common root causes such as upstream timeouts or crashes, and step‑by‑step methods to locate the problem using logs, monitoring data and configuration checks.
This article explains the purpose of TCP RST packets, how they appear during connection establishment, data transfer, firewall enforcement, and teardown, and provides practical techniques for distinguishing legitimate resets from spoofed or policy‑driven resets to improve network troubleshooting and security.
This article explains what TCP RST packets are, why they appear during connection establishment, data transfer, and termination, and how to diagnose server‑side, client‑side, and firewall‑induced resets by examining sequence diagrams, common error conditions, and TTL differences.
This article explains what TCP RST packets are, why they appear during connection establishment, data transfer, and termination, and how to analyze their causes—including server refusals, client errors, firewall policies, retransmission limits, idle timeouts, and bypass blocking—using sequence diagrams and practical diagnostics.
TCP RST packets, used to abruptly terminate or reject connections, appear at various stages—handshake, data transfer, and teardown—and can stem from server port closures, connection limits, malformed SYNs, firewall policies, timeouts, or middlebox interventions, with each scenario identifiable through detailed packet‑level analysis.
This article explains the fundamentals of TCP RST packets, distinguishes active and passive resets, outlines common kernel scenarios that generate them, and provides practical debugging methods using tcpdump, bpftrace, and source‑code analysis to resolve real‑world network incidents.
The article explains that during TCP's three‑way handshake, if a client receives a SYN‑ACK with an unexpected acknowledgment number, it must send an RST to abort the stale connection, because silently discarding the packet would cause long retransmission delays and prevent the new connection from being established.
This article explains the purpose of the TCP RST flag, how the kernel and application layers detect it, the various scenarios that trigger RST, why an RST may not terminate a connection, and the security implications of RST attacks.
This article explores three real‑world cases of TCP anomalies that affect database connectivity—ineffective RST packets, unexpected port exhaustion despite tcp_tw_reuse, and ghost connections caused by a full accept queue—explaining the underlying Linux kernel mechanics and offering practical mitigation strategies.
The article explains why a client can successfully write to a TCP socket after the server has closed its end, why the first write succeeds while the second fails, and how Linux kernel code and TCP state transitions cause this behavior.
This article explains why TIME_WAIT occurs, its resource impact, and demonstrates two optimization strategies—accelerating TIME_WAIT reclamation and using the SO_LINGER option to send an RST packet instead of the normal FIN handshake, with complete Go client and server examples and packet‑capture analysis.
This article investigates an intermittent timeout issue caused by a Java Apache HttpClient implementation that leaks connections, explains why numerous RST packets appear during TLS shutdown, and presents experiments and code revisions that clarify the TCP/TLS interaction and proper resource handling.
