AWSCRT
A high-level wrapper for the code in LibAWSCRT.jl. Currently, only an MQTT client is implemented.
Installation
pkg> add AWSCRTMQTT Client
Create a client
A client requires a TLS context that describes how the connection should (or should not) be secured.
Here, we use mutual TLS. The certificate and the private key here are those given to you by AWS IoT Core when you
create a new certificate ("Device certificate" foo.pem.crt and "Private key file" foo-private.pem.key in
the AWS Console).
tls_ctx_options = create_client_with_mtls(
ENV["CERT_STRING"],
ENV["PRI_KEY_STRING"],
ca_filepath = joinpath(@__DIR__, "certs", "AmazonRootCA1.pem"),
alpn_list = ["x-amzn-mqtt-ca"],
)
tls_ctx = ClientTLSContext(tls_ctx_options)
client = MQTTClient(tls_ctx)Connect a client
We can create a connection using the client and connect it to the MQTT endpoint (the server).
ENV["ENDPOINT"] is something like dsf9dh7fd7s9f8-ats.iot.us-east-1.amazonaws.com.
A will is not required, but we set one here.
topic = "my-topic"
connection = MQTTConnection(client)
task = connect(
connection,
ENV["ENDPOINT"],
8883,
"my-client-id";
will = Will(topic, AWS_MQTT_QOS_AT_LEAST_ONCE, "The client has gone offline!", false),
)
fetch(task) # wait for the connection to be opened (or fail)Subscribe
Once we are connected, we can subscribe to a topic(s). A callback is passed with the subscribe call; this callback is called for each received message.
topic = "test-topic"
task, id = subscribe(
connection,
topic,
AWS_MQTT_QOS_AT_LEAST_ONCE,
(topic::String, payload::String, dup::Bool, qos::aws_mqtt_qos, retain::Bool) -> begin
@info "Topic $topic received message: $payload"
end,
)
fetch(task) # wait for the server to tell us the subscription was receivedPublish
Once we are connected, we can publish a payload to a topic.
topic = "test-topic"
payload = Random.randstring(48)
task, id = publish(connection, topic, payload, AWS_MQTT_QOS_AT_LEAST_ONCE)
fetch(task) # wait for the server to tell us the published message was receivedClean Up
We can also unsubscribe and disconnect.
task, id = unsubscribe(connection, topic)
fetch(task) # wait for the server to tell us the unsubscription was received
task = disconnect(connection)
fetch(task) # wait for the connection to be closed