Many of you have asked my take on the XARA implementation of VARA HF and VARA FM. It has taken a minute but here goes.
VARA is a proprietary software modem written and distributed by José Alberto Nieto Ros (EA5HVK). Its performance and relative simplicity have made it a popular choice for both client and gateway use with Winlink, and more recently with VarAC. It remains Windows-only. José has long stated that he has no interest in developing or distributing versions for other platforms, largely because of the practical difficulty of being paid for the work.
Recently an open-source implementation of VARA HF and VARA FM appeared, written by the anonymous GitHub user x0rro and called XARA. Given that VARA is closed, commercial software confined to Windows, many in the Linux and open-source amateur-radio community had long expected that someone would eventually produce a compatible native implementation.
XARA (often stylized as xara) is an open-source, native VARA-compatible HF/FM sound modem for Linux, FreeBSD, and macOS. It is written in Rust by the anonymous developer x0rro and designed as a drop-in alternative to the official Windows VARA software, using the same TCP command/data ports (so it works with clients like Pat, Winlink Express, LinBPQ, VarAC, etc.). It includes a web UI, digipeating support, and a companion passive monitor tool. It was tested against VARA HF 4.9.0 and VARA FM 4.4.0. Copyright is listed as 2026 x0rro and it was released under the MIT license. No real name or amateur radio callsign has been publicly disclosed.
Is it part of Jose’s (EA5HVK) VARA ecosystem?
No. It is an independent project and is not affiliated with José Alberto Nieto Ros (EA5HVK). Multiple sources (including videos and the project itself) explicitly state it is not affiliated. The author has said they had no contact with EA5HVK. Community rumors of an agreement or permission were not confirmed by the developer.
Is it free?
Yes. It is free and open-source (MIT license). The unregistered version is speed-limited (similar to the free/trial version of official VARA, often cited around 177 bps). Higher “registered” speeds require compiling with a special registered feature and running with the corresponding flag, which is intended for people who already own a legitimate registration key from the original VARA developer.
A portion of the amateur-radio community believes software should always be free. That position is hard to reconcile with the reality that operators routinely pay for radios, computers, and other equipment needed to meet operational goals. Claims that it is somehow immoral for Jose to charge for his time, skill, and the creation of a tool that has become central to Winlink are not serious arguments. Developers have a right to be compensated for their work, just as manufacturers of radios and computers do.
How it was made interoperable
XARA is a from-scratch reimplementation written in Rust. The developer described the method as black-box observation of the official VARA software: studying its on-air and TCP behavior, writing a specification and a test suite based on those observations, then implementing against that specification until the tests passed and the modem interoperated with real VARA stations. The result runs natively on Linux, FreeBSD, and macOS with no Wine required.
Protocol changes and the moving target of interoperability
Jose has issued updates over the years that broke compatibility with prior versions. Examples from user reports and changelogs include:
- A late-2023 / early-2024 VARA HF update that was no longer backward-compatible with the previous three versions (related to HF APRS changes).
- Explicit notes such as the v4.8.1 KISS interface change: “This new KISS interface is no longer compatible with old versions. Update as soon as possible.”
- Earlier removal of compatibility with older 16-bit hash versions, and user reports of connection failures between mismatched versions (e.g., 4.1.x failing against 4.2.x).
Official users simply update their Windows software and continue. A third-party implementation that has achieved interoperability with a given version (as XARA did with HF 4.9.0 / FM 4.4.0) has no such path. Any subsequent protocol, framing, handshake, or speed-negotiation change can silently break it until someone reverse-engineers the new behavior and ships an update. Because the protocol is closed and not formally versioned or published, the maintainer of an open reimplementation is always one Jose release behind.
That asymmetry is inherent to the model: the original author controls the protocol and can evolve it at will, while anyone chasing interoperability is permanently reactive.
Current status (as of early November 2026)
The original GitHub repository (github.com/x0rro/xara) has been marked discontinued. The README now states that development and distribution have stopped and recommends alternatives such as mercury and openmodem. Some community forks, Windows ports by other people, and integrations (for example into SDROxide) have existed or continue independently. The author did not publicly state a specific reason for the discontinuation; speculation about legal pressure has appeared in comments, but this is unconfirmed.
Closing thoughts
The amount of work that went into XARA makes the demand for a native Linux VARA implementation clear. Many operators would also welcome a mobile version, though the practical preference for a hard-wired modem over a network connection remains. VARA continues to be used because its performance is excellent; what has been missing from Jose’s development is native support for Linux and other non-Windows platforms. This is simply an observation, not a complaint. Some argue that confining a widely used mode to a single operating system limits what amateur radio stations can do. At the same time, the absence of an officially supported version that runs on anything other than Windows remains a practical limitation. A headless micro-PC running Linux would be an attractive way to build a reliable VARA modem; the same setup on Windows introduces additional points of failure that many operators prefer to avoid for maintenance and troubleshooting reasons.
XARA may ultimately have been only a proof of concept. Because José controls the VARA protocol, a future update could prevent XARA from connecting to stations running the updated version. With the original XARA project discontinued, someone else would have to update XARA to restore interoperability. José decides how to develop and support VARA, even when others disagree with those choices.
Let me know what you think. If José offered a paid version of VARA that ran natively on Linux, would that meet your needs?
73
Julian OH8STN
If you like the work I do and want to support it, please check out one of my books. You can find them on my Amazon author page.
https://www.amazon.com/author/julian-oh8stn
Leave a Reply