Robotweax SRT 0.2.9 is available. This release improves how Backup groups resume failed paths and makes group state, selected sender paths, and RTT measurements easier to observe. It also adds optional monitoring for unused Backup paths, targeted connection-establishment changes, and updated Windows SDK installers.
Robotweax SRT remains an independent implementation of the established Secure Reliable Transport protocol. Version 0.2.9 identifies the Robotweax project; the compatible public SRT API remains 1.5.7, and the shared C ABI line remains 0.2.
More Controlled Recovery of Backup Paths
In a Backup group, a previously inactive path can now resume after the group has cumulatively acknowledged and retired an older data prefix. Recovery respects that shared progress: globally acknowledged payload is not replayed, and resuming the path does not create a new receiver sequence gap.
When a higher-priority path recovers, a now-inferior recovery probe is cancelled. If a probe fails, the next eligible path can be tried. Failed-member cleanup has also been revised: any short-lived reservation of the native UDP channel is bounded in time and count. Existing priority and stability rules remain in place. This release does not introduce automatic reconnect or RTT-driven path selection.
Four New C Queries for Connection State
Versioned, read-only C queries extend the existing API. They provide four distinct views:
- Path identifiers help correlate group paths between endpoints when enabled on both sides. These optional labels support local correlation; they do not authenticate a path.
- Normal RTT data distinguishes the measurement, its source, and its local age from an initial estimate.
- Backup sender state reports the path currently selected by the local sender and the generation of that decision. It does not by itself identify which path is delivering DATA at the receiver.
- Standby RTT results report negotiation, measurement outcome, RTT, age, and freshness for the optional monitoring service.
The four queries are additive. Previous public C exports and existing structure layouts are preserved. Applications that use internal C++ interfaces directly must be rebuilt with matching headers and library.
Standby RTT Measures Paths Without Selecting Them
Optional standby RTT monitoring measures round-trip time on unused Backup paths. It is disabled by default and requires bilateral negotiation between Robotweax endpoints in a supported Backup Live Message profile with TSBPD enabled in both directions. One-sided or unsupported configurations are rejected.
The measurements do not drive the normal RTT estimator, DATA recovery, congestion control, or Backup sender selection. A successful control-packet round trip also does not prove that a path can reliably carry DATA or provide enough bandwidth. The measurement packets are correlated but unauthenticated, even when DATA is encrypted.
Connection Establishment and Windows SDKs
Version 0.2.9 bounds the listener work involved in handing off incoming handshakes. On Linux, adoption of suitably configured native sockets is more robust; asynchronous connection rejections are processed at a paced rate. Applications still need appropriate retry and backoff policies.
Both Windows SDK installers now support upgrades within the same cryptographic backend while retaining the existing installation directory, as well as repair of the same version. A verified inventory protects user-owned files when obsolete SDK files are removed. The OpenSSL and experimental BCrypt variants were independently rebuilt, signed, and tested as the installers delivered to users.
Documentation and Downloads
Support remains scoped to the documented modes and peers. In particular, standby RTT does not establish DATA-path health, and this release does not promise lossless reconnect or behavior across every network.
The Robotweax SRT 0.2.9 release page provides the signed Windows SDKs and checksums. The release notes and compatibility overview describe the technical scope and limits.