Zenoh CPP examples

Start instructions

Depending on the backend used, the examples will be available either in examples/zenohc or examples/zenohpico (or in both, if zenoh-cpp is built for both backends) in the build directory.

Each example accepts the -h or --help option that provides a description of its arguments and their default values.

zenohc examples can work standalone, but for zenohpico examples the working zenoh router is required, so you will need to download zenoh project and run the router (Rust should be installed):

git clone https://github.com/eclipse-zenoh/zenoh
cd zenoh
cargo run

If you run the tests against the Zenoh router running in a Docker container, you need to add the -e tcp/localhost:7447 option to your examples. That's because Docker doesn't support UDP multicast transport, and therefore the Zenoh scouting and discovery mechanism cannot work with.

Examples description

Note: few examples might not be available under one of the backends, due to unsupportrd APIs.

z_scout

Scouts for Zenoh peers and routers available on the network.

Typical usage:

z_scout

z_info

Gets information about the Zenoh session.

Typical usage:

z_info

z_put

Puts a path/value into Zenoh. The path/value will be received by all matching subscribers, for instance the z_sub and z_storage examples.

Typical usage:

z_put

or

z_put -k demo/example/test -v 'Hello World'

z_pub

Declares a key expression and a publisher. Then writes values periodically on the declared key expression. The published value will be received by all matching subscribers, for instance the z_sub and z_storage examples.

Typical usage:

z_pub

or

z_pub -k demo/example/test -v 'Hello World'

z_sub

Declares a key expression and a subscriber. The subscriber will be notified of each put or delete made on any key expression matching the subscriber key expression, and will print this notification.

Typical usage:

z_sub

or

z_sub -k 'demo/**'

z_pull

Declares a key expression and a pull subscriber.
On each pull, the pull subscriber will be notified of the last N put or delete made on each key expression matching the subscriber key expression, and will print this notification.

Typical usage:

z_pull

or

z_pull -k demo/** --size 3

z_get, z_get_channel and z_get_channel_non_blocking

Sends a query message for a selector. The queryables with a matching path or selector (for instance z_queryable and z_storage) will receive this query and reply with paths/values that will be received by the receiver stream.

Typical usage:

z_get

or

z_get -s 'demo/**'

z_querier

Continuously sends query messages for a selector. The queryables with a matching path or selector (for instance z_queryable and z_storage) will receive these queries and reply with paths/values that will be received by the querier.

Typical usage:

z_querier

or

z_querier -s 'demo/**'

z_queryable

Declares a queryable function with a path. This queryable function will be triggered by each call to get with a selector that matches the path, and will return a value to the querier.

Typical usage:

z_queryable

or

z_queryable -k demo/example/queryable -v 'This is the result'

z_storage

Trivial implementation of a storage in memory. This example declares a subscriber and a queryable on the same selector. The subscriber callback will store the received paths/values in a hashmap. The queryable callback will answer to queries with the paths/values stored in the hashmap and that match the queried selector.

Typical usage:

z_storage

or

z_storage -k 'demo/**'

z_pub_shm & z_sub

A pub/sub example involving the shared-memory feature. Note that on subscriber side, the same z_sub example than for non-shared-memory example is used.

Typical Subscriber usage:

z_sub

Typical Publisher usage:

z_pub_shm

z_pub_thr & z_sub_thr

Pub/Sub throughput test. This example allows performing throughput measurements between a publisher performing put operations and a subscriber receiving notifications of those puts.

Typical Subscriber usage:

z_sub_thr

Typical Publisher usage:

z_pub_thr 1024

z_ping & z_pong

Pub/Sub roundtrip time test. This example allows performing roundtrip time measurements. The z_ping example performs a put operation on a first key expression, waits for a reply from the pong example on a second key expression and measures the time between the two. The pong application waits for samples on the first key expression and replies by writing back the received data on the second key expression.

:warning: z_pong needs to start first to avoid missing the kickoff from z_ping.

Typical Pong usage:

z_pong

Typical Ping usage:

z_ping 1024

z_pub_shm_thr & z_sub_thr

Pub/Sub throughput test involving the shared-memory feature. This example allows performing throughput measurements between a publisher performing put operations with the shared-memory feature and a subscriber receiving notifications of those puts. Note that on subscriber side, the same z_sub_thr example than for non-shared-memory example is used.

Typical Subscriber usage:

z_sub_thr

Typical Publisher usage:

z_pub_shm_thr

z_liveliness

Declares a liveliness token on a given key expression (group1/zenoh-rs by default). This token will be seen alive by the z_get_liveliness and z_sub_liveliness until user explicitly drops the token by pressing 'd' or implicitly dropped by terminating or killing the z_liveliness example.

Typical usage:

z_liveliness

or

z_liveliness -k 'group1/member1'

z_get_liveliness

Queries all the currently alive liveliness tokens that match a given key expression (group1/** by default). Those tokens could be declared by the z_liveliness example.

Typical usage:

z_get_liveliness

or

z_get_liveliness -k 'group1/**'

z_sub_liveliness

Subscribe to all liveliness changes (liveliness tokens getting alive or liveliness tokens being dropped) that match a given key expression (group1/** by default). Those tokens could be declared by the z_liveliness example. Note: the z_sub_liveliness example will not receive information about matching liveliness tokens that were alive before it's start.

Typical usage:

z_sub_liveliness

or

z_sub_liveliness -k 'group1/**'

z_bytes

Show how to serialize different message types into ZBytes, and then deserialize from ZBytes to the original message types.