rdmsm4x-changelog-20260905-1637-stop-active-screensharing-session

Identified and terminated an active Apple Remote Desktop / Screen Sharing session originating from rdmbair15m5 that was causing high WindowServer overhead and severe mouse/UI lag on rdmsm4x.

Scope

• Hosts affected: rdmsm4x, rdmbair15m5
• Service: Apple Screen Sharing (screensharingd on port 5900 / Screen Sharing.app)

Root Cause

• An established Screen Sharing connection (192.168.0.29:5900 <- 192.168.1.21:60459/64169) was active from /System/Applications/Utilities/Screen Sharing.app (PID 48051) running on rdmbair15m5.
• Active frame capture, remote cursor sync events, and SSPasteboardHelper caused screensharingd and WindowServer to consume elevated CPU (~42%), creating severe pointer lag on the physical display of rdmsm4x.
• Terminating screensharingd alone on rdmsm4x resulted in immediate auto-reconnection from rdmbair15m5.

Actions Taken

1. Traced active port 5900 connection to Screen Sharing.app on rdmbair15m5 (100.74.59.4).
2. Gracefully terminated Screen Sharing.app on rdmbair15m5 via AppleScript (osascript -e 'tell application "Screen Sharing" to quit').
3. Verified connection closure on rdmsm4x (lsof -i :5900 returned only idle listeners).
4. Verified SSPasteboardHelper exited and screensharingd dropped to 0% CPU.
5. Noted transient high CPU on 1Password.app (PID 12767) which has since returned to 0% CPU.

Verification

• pgrep -i "Screen Sharing" on rdmbair15m5 confirms application is stopped.
• lsof -i :5900 on rdmsm4x confirms no established connections.
• WindowServer CPU dropped from ~42% to normal baseline.

Undo / How to Reconnect

• Open /System/Applications/Utilities/Screen Sharing.app on rdmbair15m5 or connect to rdmsm4x.local when remote access is desired.