BACKUPS_IF_IDLE=false prevents automated backups: player check fails completely (both with and without crossplay)

[TorstenAden]

Bug Description:
When setting BACKUPS_IF_IDLE=false, the automated backups never trigger. The backup script incorrectly assumes the server is empty (0 players) and skips the backup, even when players are actively playing. This happens regardless of whether crossplay is enabled or disabled.

Environment:

• Image: lloesche/valheim-server
• Platform: Ugreen NAS (Docker)
• Network Mode: Host
• Game clients: PC

The Root Cause:
The backup script relies on checking network sockets (UDP 2456) to determine if players are online. This method no longer works reliably for modern Valheim connections in this environment. The socket check returns 0 active connections, which causes the cron job to abort.

The server log clearly registers the connections correctly:
"Player joined server "ServerName" that has join code XXXXXX, now 1 player(s)"

Expected Behavior:
The backup script should accurately detect connected players. Since checking network ports is no longer reliable for Valheim, a robust fix would be to have the script parse the valheim-server log for the current player count, rather than relying on socket checks.

[TorstenAden]

Update: The player detection issue goes both ways, making the idle-check completely unusable.

Overnight, while the server was completely empty (0 players logged in), the automated system continuously logged:
"Players connected to Valheim server - skipping update check"

Because the script falsely detected players, the BACKUPS_IF_IDLE=false condition never triggered. This resulted in backups running every 30 minutes all night long on an empty server.

It appears the current network socket check (UDP 2456/2457) cannot distinguish between actual player connections and standard background traffic (such as continuous A2S_INFO server browser pings from Steam master servers).

Relying on network socket monitoring for player detection is broken in both directions (false negatives during active Crossplay/PlayFab sessions, and false positives from server pings when empty). Parsing the actual server log for player count is strongly recommended to resolve this completely.