[BornToBeRoot]

Review of the IP Scanner and Port Scanner (bugs, behaviour, performance), fixed one commit per finding.

Bug fixes (IP Scanner + Port Scanner)

• A scan ends exactly once (completed, canceled or failed): the tab no longer gets stuck when canceled right before the scan starts or on an unexpected error. "Canceled by user" and "hostnames could not be resolved" are no longer replaced by "No reachable hosts / open ports found".
• Port probe: only a refused connection is closed, no answer is timed out (before every error was closed); connections are closed with a reset, so open ports no longer pile up TIME_WAIT sockets and exhaust the local ports.
• Closed ports are reported immediately: Windows repeated the connection request after a reset and reported it after ~2 s (= the new default timeout, so closed ports showed as timed out). SYN retransmissions are disabled per socket (SIO_TCP_INITIAL_RTO, RTO = timeout); new Attempts setting (default 1) to retry ports without answer on unreliable networks.
• Overlapping inputs are scanned once (e.g. 10.0.0.1; 10.0.0.0/24, also Ping Monitor), different hostnames of one IP are kept; ports are scanned once (80; 1-100).
• Very large inputs: confirmation above 65,536 IP addresses (Port Scanner: hosts × ports), refused above 16,777,216 instead of running out of memory (/1).
• IP ranges across 128.0.0.0 are accepted by the validator.
• Port Scanner: sorting by IP address with multiple hosts crashed the app; results are sorted by IP and port.
• ICMP buffer limited to 65500 bytes (IP Scanner, Ping Monitor, Traceroute) - above, every host was "unreachable".

IP Scanner

• ICMP Attempts were ignored (first lost ping = host down).
• A host that blocks ICMP but refuses a port (TCP reset) is detected as up.
• NetBIOS column sort / visibility, Copy menu visibility, Copy > Status copies Up/Down.
• Custom commands: {{Hostname}} (from DNS/NetBIOS, i.e. from the network) is only used if it's a valid hostname (command injection, e.g. & with cmd.exe /c); Edit/Delete need a selection.
• MAC address: neighbor table read once per scan (refresh only when needed) instead of per host, only for hosts in a local subnet; own IPv6 / link-local addresses. Resolve MAC address enabled by default for new installations (as documented).
• NetBIOS: only the answer of the scanned host is accepted; response without MAC block keeps the names.

Performance

• New defaults: timeouts 4000 → 2000 ms, IP Scanner 128 hosts × 16 ports (all default ports at once; max 256 × 32), Port Scanner 4 × 128. Settings still on an old default are migrated. Empty /24: ~9 s instead of ~50 s.
• The first hosts / ports of a scan are started one after another (10 ms / 1 ms) instead of ~1400 connection requests at once, afterwards without delay.
• Port probe and NetBIOS without exceptions (SocketAsyncEventArgs) - the app no longer lags while scanning with a debugger attached.
• Host range expansion without parallel bag + full sort, allocation-free IP compare, export in the background (in the order shown in the grid).

Docs: settings (defaults, ranges, attempts, threads/firewall note), context menu, result, keyboard shortcuts.

To-Do

• Update documentation to reflect this changes
• Update changelog to reflect this changes

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