Quickstart¶

A three-terminal pub/sub loop.

1. Discovery daemon¶

cortex-discovery

Leave it running. This is the service that maps topic names to IPC endpoints.

2. Publisher¶

pub.py

import numpy as np
import cortex
from cortex import Node
from cortex.messages.standard import ArrayMessage


class SensorNode(Node):
    def __init__(self):
        super().__init__("sensor")
        self.pub = self.create_publisher("/sensor/data", ArrayMessage)
        self.count = 0
        self.create_timer(0.1, self.tick)  # 10 Hz

    async def tick(self):
        data = np.random.randn(64, 64).astype("float32")
        self.pub.publish(ArrayMessage(data=data, name=f"frame_{self.count}"))
        self.count += 1


async def main():
    node = SensorNode()
    try:
        await node.run()
    finally:
        await node.close()


if __name__ == "__main__":
    cortex.run(main())

python pub.py

3. Subscriber¶

sub.py

import cortex
from cortex import Node
from cortex.messages.base import MessageHeader
from cortex.messages.standard import ArrayMessage


async def on_data(msg: ArrayMessage, header: MessageHeader):
    print(f"[{header.sequence}] {msg.name} shape={msg.data.shape}")


class ViewerNode(Node):
    def __init__(self):
        super().__init__("viewer")
        self.create_subscriber("/sensor/data", ArrayMessage, callback=on_data)


async def main():
    node = ViewerNode()
    try:
        await node.run()
    finally:
        await node.close()


if __name__ == "__main__":
    cortex.run(main())

python sub.py

What happened¶

sequenceDiagram
    participant P as Publisher
    participant D as Discovery daemon
    participant S as Subscriber

    P->>D: REGISTER /sensor/data -> ipc:///tmp/cortex/topics/...
    S->>D: LOOKUP /sensor/data
    D-->>S: ipc:///tmp/cortex/topics/...
    S->>P: ZMQ SUB connect + SUBSCRIBE "/sensor/data"
    loop 10 Hz
        P->>S: multipart frames: topic, header, metadata, buffer
        S->>S: decode + await on_data(msg, header)
    end

Next: Concepts → Architecture or Tutorials → Custom messages.