Loopback tests for the network threads (#106) (#124)

* test: pin the Win-Test sked frames over a loopback socket (#106)

WinTestSkedSender is pointed at the loopback address instead of a
broadcast address, and a socket on an ephemeral port receives the
LOCKSKED/ADDSKED/UNLOCKSKED sequence. The frames and their checksum
byte are written out literally, including the \260 degree escape and
the SSB fallback for an unexpected mode ID.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: cover the PSTRotator UDP client over loopback (#106)

A socket on an ephemeral loopback port plays PSTRotator. The tests pin
the poll queries, the <PST> command frames, the AZ:/EL:/MODE: replies
reaching the listener, an unparsable reply leaving the loop alive, and
the explicit-port constructor reporting its status after start() (#115).
The reply format is derived from the parser and the PSTRotator UDP
documentation, not from a capture.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: cover the AirScout UDP listener over loopback (#106)

ReadUDPbyAirScoutMessageThread gains a package-private constructor that
takes an already bound socket, as ReadUDPbyUCXMessageThread has; the
public constructor still binds the configured port in run(). The tests
pin applying an ASNEAREST response to every active variant of the
receiver, the case-sensitive server/client match with a UTF-8 client
name, the disabled listener, the poison pill, recovery from a malformed
response, and the date losing its space because the parser strips all
spaces.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: cover UCXLog/DXLog QSO packets over loopback (#106)

The UCX loopback test now sends contactinfo and contactreplace packets:
transport bytes before the XML are dropped, the QSO reaches the
controller with band, locator and source, the gross field is
registered, an unknown station is stored in the database and the UDP
backup file, a known one is only updated, and nothing happens while log
sync is disabled. A RadioInfo packet sent afterwards serves as an
ordering marker instead of a sleep.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: cover the local DX Cluster server over loopback (#106)

DXClusterThreadPooledServer gains a package-private constructor that
takes an already bound server socket; the public constructor still binds
the configured port in run(). Plain sockets on the loopback address act
as logging programs. The tests pin the listening status, the "login: "
prompt, one DXSpider-style line with BEL BEL CR LF per spot to every
client, the rejection of spots that cannot be formatted, and stop()
closing the clients and ending the server thread.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix: keep the UCXLog/DXLog listener alive on bad input (#106)

An unwritable or empty backup path left the FileWriter null, and the
following BufferedWriter threw a NullPointerException; a RadioInfo
without <Freq> or <Mode> threw one as well. Neither was caught, so the
listener thread ended for good. The backup line is now written with
try-with-resources and skipped with a log line when the file cannot be
opened, an incomplete RadioInfo element is skipped, and run() drops a
packet whose processing throws any RuntimeException, reports a
non-critical status and keeps receiving.

The loopback tests cover all three paths. The interrupt test now waits
for a processed marker packet instead of sleeping and no longer claims
more than it can observe, and the marker helper states its in-order
assumption for UDP on loopback.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix: let a second DX Cluster server run() bind again (#106)

The pre-bound-socket constructor made run() skip binding whenever a
server socket existed. A run() after the first one ended would then
accept on a closed socket. Bind whenever the socket is missing or
closed, which restores the behaviour of the public constructor.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: make the ignored AirScout responses observable (#106)

The tests for responses to another client or server and for the
disabled listener only checked that nothing happened before the poison
pill, which a listener that never read the datagrams would also pass.
Each now sends a valid sentinel afterwards and waits for it, and the
ignored responses name a different receiver, so a wrongly processed
copy is detectable; the disabled case also shows that the switch was
asked once per response. The date test is renamed and documented as a
pinned known defect, so a parser fix knows to flip it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test: wait for the PSTRotator listener thread after stop() (#106)

The client keeps its listener thread private, so the test finds it by
the name start() gives it and joins it after stop(), asserting that
exactly one such thread existed and that it ended.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix: keep the UCX listener alive when the status callback throws (#106)

Review follow-up. The safety net reported a dropped packet through the
status callback without guarding it, so a throwing callback still ended
the listener. The test for an unwritable backup file is renamed to what
it proves, and the changelog mentions that any unexpected error now
drops only the affected packet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

github_docs/de-Changelog.md

@@ -50,6 +50,8 @@ Mehrere Operateure an einem Rechner können jetzt eigene Rufzeichen, Locators un
 
 - **UCXLog-Pakete werden nicht mehr abgeschnitten:** Nach einem kurzen UDP-Paket las der Empfänger für UCXLog-kompatible Logprogramme jedes längere Folgepaket nur bis zur Länge des kurzen, sodass Logeinträge unvollständig ankommen konnten. Außerdem schließt das Trennen den Socket des Empfängers jetzt sofort, statt bis zum nächsten Timeout zu warten. UCXLog-Pakete und Antworten von AirScout werden jetzt immer als UTF-8 dekodiert statt im Standardzeichensatz des Systems, sodass Umlaute in Stationsnamen und Operator-Rufzeichen unter Windows nicht mehr verstümmelt ankommen. Damit ist [Issue #115](https://github.com/praktimarc/kst4contest/issues/115) behoben.
 
+- **UCXLog/DXLog-Empfänger läuft weiter:** Eine nicht beschreibbare Sicherungsdatei für empfangene QSOs oder ein RadioInfo-Paket ohne Frequenz oder Betriebsart hielt den Empfänger für UCXLog-kompatible Logprogramme bis zum nächsten Neustart an, sodass weder gearbeitete Stationen noch QRG-Änderungen ankamen. Jetzt wird der Sicherungseintrag beziehungsweise das unvollständige Paket übersprungen, und der Empfänger empfängt weiter. Jeder andere unerwartete Fehler beim Verarbeiten eines Pakets verwirft jetzt nur dieses Paket und erscheint als Statusmeldung, statt den Empfänger anzuhalten.
+
 ### Hinweise zur Aktualisierung
 
 - Bestehende Installationen werden **nicht** verändert: `preferences.xml` und `praktiKST.db` bleiben genau dort liegen, wo sie sind, und werden zum Profil **Default**. Es wird keine Datei verschoben oder kopiert.