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You will maintain and further develop HWS J-Term, an established Windows terminal emulator for IBM mainframes (3270), IBM i (5250) and Unix systems (VT / SSH), which are used in business-critical client environments.

What to expect: a mature Java system with ~370,000 lines of code and an AWT-based user interface, byte-level binary terminal protocols, native Windows integration and very low test coverage. No Spring, no cloud, no microservices. In return: a technically sophisticated, functionally unique product, genuine ownership and a clear modernisation mandate.

Your responsibilities

Root cause analysis and troubleshooting across the protocol, rendering and API layers
Setting up automated test coverage for the protocol implementations
Rectifying identified security vulnerabilities (TLS / SSH / credentials)
Incremental modernisation of the architecture and build system without breaking compatibility
Analysing customer issues from network logs

Your profile

At least 7 years’ experience with Java, including 3+ years working on mature legacy systems
In-depth knowledge of multithreading, socket programming and byte/bit-level processing
Confidence in using AWT / Swing and the Event Dispatch Thread
Experience with TLS / JSSE and SSH
Windows development environment, basics of JNA/JNI
Maven and Ant; willingness to set up a CI pipeline
Experience with legacy refactoring and characterisation tests

Desirable

Knowledge of the IBM 3270/5250 or DEC VT protocols, HLLAPI, EBCDIC
Experience with terminal emulation or host connectivity products
Ability to read C / C++, COM/DDE
Eclipse RCP / OSGi

Senior Java Engineer

Job Description