opcda-bridge-gateway

Windows gateway that exposes native OPC DA (COM/DCOM) servers over the network to opcda-bridge-client and other gRPC clients.

Install it with Cargo on a Windows host:

cargo install opcda-bridge-gateway

The gateway is versioned independently from the client and protocol crates. Prebuilt archives use opcda-bridge-gateway-vX.Y.Z tags; client/gateway interoperability is determined by the wire protocol and advertised capabilities rather than matching package versions.

The gateway-wide GetGatewayInfo RPC advertises the protocol-feature ranges supported by the running binary without opening an OPC DA server. The client compatibility command uses this handshake for deployment checks; GetCapabilities remains the per-server operational capability endpoint and supports older clients.

The gateway must run on the Windows machine hosting the OPC DA server. See the repository README for service installation, configuration, and firewall setup.

Tag browsing uses native one-level OPC DA enumeration with bounded pages. The gateway owns opaque browse sessions and continuation tokens, preserves exact ItemIDs separately from display names, and reports whether a page is complete. Only selectable item and branch-and-item nodes expose ItemIDs; branch-only nodes retain their private navigation identifiers behind opaque node keys. Namespace search is a bounded progressive operation that can be cancelled by dropping the client stream. DA3 root ItemIDs and unused filters are sent as required non-null empty strings. A server that also supports DA2 falls back only when its first DA3 root browse returns RPC_X_NULL_REF_POINTER or E_NOTIMPL, and reports that compatibility decision explicitly.

The gateway also exposes persistent indexed-search status, refresh, pause, resume, cancel, and query operations for explicitly configured OPC servers. Capability responses advertise indexed search support, its protocol version, the configured result limit, and the server's index state. Indexed results contain exact ItemIDs and breadcrumb labels, never browse-session node keys. Refreshes run asynchronously, and gateway shutdown cancels active indexing before the process exits. An inventory can complete successfully with a non-fatal warning when the OPC server rejects specific namespace branches; the generation remains active and usable, and the status diagnostic is reported as a warning unless the index state is failed. Completed active generations are durable across gateway restarts. Activation is a short atomic metadata transition, so search and status remain responsive while a refresh becomes active. Superseded and abandoned data is reclaimed in bounded background batches through a separate SQLite WAL connection. An interrupted refresh is superseded when a complete active generation remains available, so status and search continue to use that snapshot while cleanup runs. An interrupted initial build remains failed and visible because no complete snapshot can replace it.

Read responses contain semantic values. For an OPC DA VT_BSTR, the gateway forwards the exact BSTR contents without adding display quote characters; quotes remain only when present in the server value.

Read responses contain semantic values. For an OPC DA VT_BSTR, the gateway forwards the exact BSTR contents without adding display quote characters; quotes remain only when present in the server value.

Configure the index in the gateway TOML file under [index]. Automatic indexing is restricted to the explicit servers allow-list and uses a service-writable SQLite database, conservative batch/rate/duty-cycle defaults, a two-second foreground quiet period, and one build at a time. The default database path is %PROGRAMDATA%\\opcda-bridge\\index.sqlite3 on Windows and $XDG_DATA_HOME/opcda-bridge/index.sqlite3 (falling back to $HOME/.local/share/opcda-bridge/index.sqlite3) on Linux/macOS. See the example file for all available settings, including maintenance windows and health thresholds.