Experience NATS Core

Prerequisites: Start the Broker

Follow Quick Install to install RobustMQ, then start the service:

robust-server start

RobustMQ starts NATS on port 4222 by default — no extra configuration needed.

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Install NATS CLI

# macOS
brew install nats-io/nats-tools/nats

# Linux / Windows
# See: https://docs.nats.io/using-nats/nats-tools/nats_cli

Set the server URL (optional, avoids typing --server each time):

export NATS_URL=nats://localhost:4222

Verify the connection:

nats server ping

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Pub/Sub

The simplest publish-subscribe pattern.

# Terminal 1: subscribe
nats sub "hello.>"

# Terminal 2: publish
nats pub hello.world "Hello RobustMQ!"
nats pub hello.nats  "NATS is working!"

Terminal 1 receives both messages immediately. > is a wildcard that matches all tokens under hello..

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Request-Reply

Synchronous request-response — ideal for RPC scenarios.

# Terminal 1: start a service that replies to requests
nats reply orders.query '{"status":"ok"}'

# Terminal 2: send a request and wait for the reply
nats request orders.query '{"id":"001"}'

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Queue Groups (competing consumers)

Multiple consumers join the same Queue Group. Each message is delivered to exactly one of them, providing load balancing.

# Terminals 1, 2, 3: start three workers in the same Queue Group
nats sub orders.created --queue order-processors   # Worker 1
nats sub orders.created --queue order-processors   # Worker 2
nats sub orders.created --queue order-processors   # Worker 3

# Terminal 4: publish messages (each goes to exactly one worker)
nats pub orders.created '{"order_id":"001"}'
nats pub orders.created '{"order_id":"002"}'
nats pub orders.created '{"order_id":"003"}'

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Messages with Headers

nats pub --header "Content-Type:application/json" \
         --header "X-Trace-ID:abc123" \
         orders.created '{"order_id":"001"}'

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Next Steps

• NATS Core Reference — protocol details, wildcards, auth, TLS, and more
• SDK Integration — client library links for all languages
• Experience mq9 — AI Agent communication protocol built on NATS