Turning Off Echo’d Messages

    The NoEcho option can be useful in BUS patterns where all applications subscribe and publish to the same subject. Usually a publish represents a state change that the application already knows about, so in the case where the application publishes an update it does not need to process the update itself.

    Keep in mind that each connection will have to turn off echo, and that it is per connection, not per application. Also, turning echo on and off can result in a major change to your applications communications protocol since messages will flow or stop flowing based on this setting and the subscribing code won’t have any indication as to why.

    {% tabs %} {% tab title=”Go” %}

    {% tab title=”Java” %}

    2.                             server("nats://demo.nats.io:4222").
    3.                             noEcho(). // Turn off echo
    4.                             build();
    5. Connection nc = Nats.connect(options);
    7. // Do something with the connection
    9. nc.close();

    {% endtab %}

    {% tab title=”JavaScript” %}

    {% endtab %}

    1. ncA = NATS()
    2. ncB = NATS()
    4. await ncA.connect(no_echo=True)
    5. await ncB.connect()
    6. async def handler(msg):
    7.    # Messages sent by `ncA' will not be received.
    8.    print("[Received] ", msg)
    10. await ncA.subscribe("greetings", cb=handler)
    11. await ncA.flush()
    12. await ncA.publish("greetings", b'Hello World!')
    13. await ncB.publish("greetings", b'Hello World!')
    15. # Do something with the connection
    17. await asyncio.sleep(1)
    18. await ncA.drain()

    {% endtab %}

    {% tab title=”Ruby” %}

    {% endtab %}

    {% tab title=”C” %}

    1. natsOptions         *opts    = NULL;
    2. natsStatus          s        = NATS_OK;
    4. s = natsOptions_Create(&opts);
    5. if (s == NATS_OK)
    6.     s = natsOptions_SetNoEcho(opts, true);
    7. if (s == NATS_OK)
    8.     s = natsConnection_Connect(&conn, opts);
    10. (...)
    12. // Destroy objects that were created
    14. natsOptions_Destroy(opts);