Send and receive normal messages by using the TCP client SDK for C/C++ - ApsaraMQ for RocketMQ

Normal messages in ApsaraMQ for RocketMQ have no special delivery semantics -- they differ from scheduled, delayed, ordered, and transactional messages.

Important

Each topic supports only one message type. A topic created for normal messages cannot send or receive other message types.

The following sections walk through sending and receiving normal messages with the TCP client SDK for C/C++.

Prerequisites

Before you begin, make sure that you have:

Downloaded the SDK for C/C++
Prepared your environment (V1.x.x)
Created the required resources -- an instance, a topic, and a consumer group -- in the ApsaraMQ for RocketMQ console
Created an AccessKey pair for your Alibaba Cloud account

Send normal messages

The following example creates a producer, connects to the broker, and sends a single normal message.

Replace the placeholders in the code with your actual values:

Placeholder	Description	Where to find it
`<your-group-id>`	Producer group ID	ApsaraMQ for RocketMQ console
`<your-tcp-endpoint>`	TCP endpoint URL	TCP Endpoint section on the Instance Details page
`<your-topic>`	Topic name	ApsaraMQ for RocketMQ console
`<your-message-content>`	Message body content	Defined by your application

#include "ONSFactory.h"
#include "ONSClientException.h"

using namespace ons;

int main()
{
    // Configure producer properties
    ONSFactoryProperty factoryInfo;
    factoryInfo.setFactoryProperty(ONSFactoryProperty::ProducerId, "<your-group-id>");
    factoryInfo.setFactoryProperty(ONSFactoryProperty::NAMESRV_ADDR, "<your-tcp-endpoint>");
    factoryInfo.setFactoryProperty(ONSFactoryProperty::PublishTopics, "<your-topic>");
    factoryInfo.setFactoryProperty(ONSFactoryProperty::MsgContent, "<your-message-content>");

    // Load credentials from environment variables.
    // Make sure ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are set.
    factoryInfo.setFactoryProperty(ONSFactoryProperty::AccessKey, getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"));
    factoryInfo.setFactoryProperty(ONSFactoryProperty::SecretKey, getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET"));

    // Create and start the producer.
    // Call start() exactly once before sending any messages.
    Producer *pProducer = ONSFactory::getInstance()->createProducer(factoryInfo);
    pProducer->start();

    // Build the message
    Message msg(
            factoryInfo.getPublishTopics(),  // Topic (must be a normal-message topic)
            "TagA",                          // Tag -- consumers use tags to filter messages
            factoryInfo.getMessageContent()  // Body -- cannot be empty
    );

    // Set a message key for traceability.
    // Keys must be globally unique whenever possible (for example, an order ID).
    // Use the key to look up messages in the ApsaraMQ for RocketMQ console.
    msg.setKey("ORDERID_100");

    // Send the message. If no exception is thrown, the message is sent.
    try
    {
        SendResultONS sendResult = pProducer->send(msg);
    }
    catch(ONSClientException & e)
    {
        // Handle the send failure (log, retry, alert, etc.)
    }

    // Shut down the producer before your application exits to prevent issues such as memory leaks.
    pProducer->shutdown();

    return 0;
}

Message properties

Property	Details
Tag	A secondary classifier on each message. Consumers use tags to filter messages at the broker side, so only relevant messages are delivered.
Key	A business identifier (such as an order ID) that must be globally unique whenever possible. Use it to query specific messages in the ApsaraMQ for RocketMQ console. Setting a key is optional -- messages can be sent and received without one.
Body	The message payload. ApsaraMQ for RocketMQ does not process or parse the body. Producer and consumer must agree on the serialization and deserialization format. The body cannot be empty.

Producer lifecycle

Phase	Method	Notes
Start	`pProducer->start()`	Call once before sending any messages.
Send	`pProducer->send(msg)`	If no exception is thrown, the message is sent.
Shut down	`pProducer->shutdown()`	Call before the application exits. Skipping this step may cause issues such as memory leaks.

Subscribe to normal messages

For consumer setup and sample code using the TCP client SDK for C/C++, see Subscribe to messages.