Technical writing about VPN server monitoring, protocol-specific pitfalls, and infrastructure observability. Occasionally opinionated.
Most posts here come from real incidents we ran into building TunnelHQ — the kind that show why a TCP port check on a WireGuard endpoint, an OpenVPN TLS handshake, or a V2Ray subscription URL will lie to you about whether the server actually works. We try to keep each post grounded in the protocol on the wire (handshakes, framing, key rotation) and useful to operators running real fleets, not marketing-style overviews.
If you maintain VPN servers and want a deeper read on protocol-aware monitoring, the per-protocol guides are a good starting point: WireGuard, OpenVPN, VLESS, VMess, Trojan, Shadowsocks, and Hysteria2. Or run an ad-hoc check via the free config tester.
You typed that error into Google and landed here. Eight things that actually cause it, ordered from most common to least, with the commands to check each. UDP blocking, cert expiry, TLS-auth mismatch, and five more.
Subscription URLs sound simple until you run a fleet. Stale caches, partial deliveries, dead servers inside healthy bundles, drift between clients. A practical checklist for monitoring Xray and V2Ray subscription URLs in production, plus a war story about the 47 dead servers nobody knew about.
A WireGuard server on UDP/51820 will look perfectly healthy to UptimeRobot, Better Stack, or any generic port monitor even when every client is getting connection failures. Here's what's actually happening on the wire, and how to catch real failures.