Senior Java Engineer – Terminal Emulation & Host Connectivity

Are you a senior Java engineer who enjoys solving complex technical problems and working with systems where there is no “off-the-shelf” answer? At HWS Technologies, we’re looking for a Senior Java Engineer to join our team and take ownership of the continued development and modernisation of HWS J-Term — an established Windows terminal emulator used in business-critical client environments. This is not your typical Java/Spring/cloud role. You’ll be working deep in the stack: terminal protocols, networking, concurrency, rendering, security and native Windows integration. 💻 What you’ll be working with HWS J-Term is a mature Java application with approximately 370,000 lines of code, an AWT-based user interface and implementations of: • IBM mainframe 3270 terminal protocols • IBM i 5250 terminal protocols • Unix VT / SSH connectivity • Byte-level binary protocols • Native Windows integration There’s no Spring, no cloud and no microservices. Instead, you’ll have the opportunity to work on a technically sophisticated, functionally unique product with genuine ownership and a clear modernisation mandate. 🔧 Your responsibilities • Perform root cause analysis and troubleshooting across protocol, rendering and API layers • Build automated test coverage for protocol implementations • Identify and rectify security vulnerabilities, particularly around TLS, SSH and credentials • Incrementally modernise the architecture and build system while maintaining compatibility • Analyse customer issues using network logs and technical diagnostics • Contribute to improving the maintainability, reliability and security of the product 🧑‍💻 What we’re looking for You’ll ideally bring: • 7+ years of professional Java experience, including 3+ years working with mature/legacy systems • Strong knowledge of multithreading, socket programming and byte/bit-level processing • Confidence working with AWT/Swing and the Event Dispatch Thread • Experience with TLS/JSSE and SSH • Experience developing in a Windows environment • Basic knowledge of JNA/JNI • Experience with Maven and Ant • Willingness and ability to establish or improve CI pipelines • Practical experience with legacy refactoring and characterisation testing • A problem-solving mindset and the ability to understand complex systems without relying on modern frameworks ⭐ Nice to haveIt would be a strong advantage if you have experience with: • IBM 3270 / 5250 or DEC VT protocols • HLLAPI or EBCDIC • Terminal emulation or host connectivity products • Reading C/C++ code • COM/DDE • Eclipse RCP / OSGi 🌟 Why join HWS?This is an opportunity to work on a product where your technical decisions genuinely matter. You’ll have the chance to: 🔹 Take real ownership of a unique and established product 🔹 Work on challenging low-level Java and networking problems 🔹 Modernise a mature system without sacrificing compatibility 🔹 Improve security, testing and engineering practices 🔹 Work with an experienced international technology team 🔹 Make a tangible impact on a business-critical product If you’re a Senior Java Engineer who enjoys understanding how things really work under the hood, we’d love to hear from you.