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Session-based ON4KST connection lifecycle: Each socket, reader, writer, message bus and queue now belongs to an explicitly identified connection session. Delayed threads from an obsolete connection can therefore no longer process data or close its replacement. ONLINE is reported only after the login has been accepted and all requested user lists have been received. Connection setup, login and synchronisation use bounded timeouts, while heartbeats, missing inbound traffic, EOF and read or write failures trigger controlled reconnect attempts with backoff where appropriate. Validated ON4KST protocol commands: Outgoing frames are built centrally and checked for valid categories, locators and prohibited frame delimiters. Because ON4KST maintains one locator per TCP session, the main locator is used for both chat categories and a conflicting secondary configuration is logged instead of sending contradictory commands to the server.
KST4Contest
KST4Contest is a Java-based client for the ON4KST chat, developed for coordinated VHF, UHF and microwave contest operation.
The application is developed by Marc Fröhlich (DO5AMF) and since 2026 Philipp Wagner (DN9APW).
Start here
- Project website
- Download Stable, Beta and Nightly builds
- Online manual
- GitHub wiki
- Issues and bug reports
- Development roadmap
What KST4Contest does
KST4Contest combines the ON4KST chat with information that is useful when coordinating contacts during a contest.
Among other things, it can:
- display and filter stations from the supported ON4KST chat categories;
- derive band and frequency information from chat messages and station names;
- maintain Worked and NOT QRV information for the available bands;
- calculate station priorities from distance, activity and other available information;
- manage internal skeds and received Win-Test skeds;
- use AirScout information when evaluating possible aircraft-scatter contacts;
- display stations, paths and additional propagation information on maps;
- exchange information with supported logging programs, Win-Test, PSTRotator and a local DX Cluster interface;
- provide configurable automatic replies for recurring chat requests.
Calculated scores, aircraft-scatter information and path assessments are operating aids. They depend on the available data and should not be treated as guarantees that a contact is possible.
Installation
Ready-to-use packages are available for Windows, Linux and macOS. These packages include the required Java runtime, so a separate Java installation is normally not necessary.
Use the central download page to select the appropriate build:
- Stable is intended for normal contest operation.
- Beta contains changes that are being prepared for a stable release.
- Nightly contains the latest automated development build and is mainly intended for testing.
Documentation
The documentation is available in German and English:
The Markdown sources used for the wiki and the generated PDF manuals are stored in github_docs.
Changes to operating behaviour should be documented together with their purpose and limitations. This is especially important for functions whose result depends on external data, heuristics or information derived from chat messages.
Building from source
Building KST4Contest requires JDK 21. The Maven Wrapper included in the repository should be used, so a separate Maven installation is not required.
Linux and macOS:
./mvnw clean test
./mvnw -B -DskipTests compile
Windows:
mvnw.cmd clean test
mvnw.cmd -B -DskipTests compile
Repository structure
src/main/java/– application source codesrc/test/– automated testsgithub_docs/– German and English manual sourceswebsite/– project website sourcespackaging/– platform-specific packaging files
CI status
Documentation
Builds
License
KST4Contest is distributed under the GNU General Public License v3.0.