event_based_communication

Event-Based Communication

Caution

Every payload you transmit with iceoryx2 must be compatible with shared memory. Specifically, it must:

• be self contained, no heap, no pointers to external sources
• have a uniform memory representation, ensuring that shared structs have the same data layout
  • therefore, only ctypes and ctypes.Structure can be transferred
• not use pointers to manage their internal structure

Any other python data type, except ctypes or ctypes.Structures, will likely cause undefined behavior and may result in segmentation faults.

Only fixed-size integers (like ctypes.c_uint8_t), ctypes.c_float, ctypes.c_double, and the types in the iceoryx2-bb-container library are cross-language compatible!

This example is a minimal Python version of the Rust/C++ event_based_communication example. It combines:

• publish_subscribe for transporting TransmissionData
• event for signaling state changes
• waitset for event-driven processing

The publisher emits one sample every second and notifies SentSample (event id 4). The subscriber reacts to this event, drains all available samples, and sends back ReceivedSample (event id 5) as an acknowledgement.

How to Build

Before proceeding, a virtual environment with all dependencies needs to be created. You can find the detailed instructions in the Python Examples Readme.

poetry --project iceoryx2-ffi/python install

Then, the iceoryx2 python bindings can be built and installed into the virtual environment:

poetry --project iceoryx2-ffi/python run maturin develop --manifest-path iceoryx2-ffi/python/Cargo.toml --target-dir target/ff/python

How to Run

To observe this communication in action, open two terminals and execute the following commands:

Terminal 1

poetry --project iceoryx2-ffi/python run python examples/python/event_based_communication/subscriber.py

Terminal 2

poetry --project iceoryx2-ffi/python run python examples/python/event_based_communication/publisher.py

Tip

You may hit the maximum supported number of ports when too many publisher or subscriber processes run. Take a look at the iceoryx2 config to set the limits globally or at the API of the Service builder to set them for a single service.