Module troubleshooting 

Troubleshooting

Message too large / truncated

Messages pass through multiple buffer layers. A message must fit every layer to be delivered intact:

Layer	Env var	Posix default
Defragmentation	NROS_ZENOH_FRAG_MAX_SIZE	65536
Batch size	NROS_ZENOH_BATCH_UNICAST_SIZE	65536
Shim buffer	NROS_SUBSCRIBER_BUFFER_SIZE	1024
User receive buffer	— (const generic)	1024

For large messages, increase the transport limits (set before cargo build) and size the per-entity buffer via the builder’s .rx_buffer::<N>():

// 4 KB receive buffer
executor.node_mut(node).subscription("/topic").typed::<MyMsg>()
    .rx_buffer::<4096>().build(|msg| { ... })?;

zenoh version mismatch

zenoh-pico and zenohd must be the same version (1.6.2). Symptoms: z_publisher_put failed: -100 (_Z_ERR_TRANSPORT_TX_FAILED) followed by -73 (_Z_ERR_SESSION_CLOSED).

The router is the one ROS ships: ros2 run rmw_zenoh_cpp rmw_zenohd. nano-ros vendors none (RFC-0075), and the old just build-zenohd recipe was retired with the vendored copy.

Build issues

• Submodule not found — init that ONE submodule, scoped: git submodule update --init packages/rmw/zenoh/zpico-sys/zenoh-pico. Never --recursive on nano-ros — the transitive closure is large and mostly irrelevant to any one task. nros setup <board> --rmw zenoh provisions it for you, shallow, and is the preferred route.
• CMake cache stale (changed env vars not taking effect) — run cargo clean -p zpico-sys then rebuild

zenoh-pico error codes

Code	Name	Meaning
-3	_Z_ERR_TRANSPORT_OPEN_FAILED	Cannot connect to router
-73	_Z_ERR_SESSION_CLOSED	Session closed after failure
-78	_Z_ERR_SYSTEM_OUT_OF_MEMORY	Allocation failed
-100	_Z_ERR_TRANSPORT_TX_FAILED	Transport transmission failed
-128	_Z_ERR_GENERIC	Generic error