THE actual root cause of the flicker-then-blank / "connected but drops" RDP
behavior. guacamole-common-js's WebSocketTunnel sends an internal stability
"ping" (empty INTERNAL_DATA_OPCODE: `0.,4.ping,<ts>;`) and resets its
receiveTimeout only on inbound data. guacamole-lite 1.2.0 forwards that ping
straight to guacd, which neither understands nor echoes it. On an idle desktop
(no frames flowing), nothing resets the client timer, so the tunnel hits
UPSTREAM_TIMEOUT, closes, and reconnects — the flicker/drop loop seen in guacd
as "User is not responding".
Fix: intercept the internal ping on the WS in guacamole.ts and echo it straight
back to the client before ClientConnection forwards it to guacd, so the client's
stability timer is satisfied even when the remote desktop is idle.
Verified separately: a guacd connection that echoes sync held 30s/116 syncs with
no drop; server/xrdp/XFCE are healthy. This was purely the missing ping echo.
Co-authored-by: Samuel James <ssamjame@amazon.com>
Co-authored-by: Kiro <noreply@kiro.dev>
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