Send logs to DataDog using Logback yierds "Log destination intake.logs.datadoghq.com/<unresolved>:10514: connection failed. "

Question

I wish to send logs to DataDog following this tutorial which is the "Agentless" way of sending logs.

I do not wish to use any agent, going via logstash or any other system.

I am following the guide, unfortunately, I am facing

20:39:26,617 |-WARN in net.logstash.logback.appender.LogstashTcpSocketAppender[JSON_TCP] - Log destination intake.logs.datadoghq.com/<unresolved>:10514: connection failed. java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@576302b[Not completed, task = net.logstash.logback.appender.AbstractLogstashTcpSocketAppender$TcpSendingEventHandler$ReaderCallable@622eaf6d] rejected from java.util.concurrent.ScheduledThreadPoolExecutor@3403e2ac[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0]
    at java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@576302b[Not completed, task = net.logstash.logback.appender.AbstractLogstashTcpSocketAppender$TcpSendingEventHandler$ReaderCallable@622eaf6d] rejected from java.util.concurrent.ScheduledThreadPoolExecutor@3403e2ac[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0]
    at  at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2081)
    at  at java.base/java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:841)
    at  at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:340)
    at  at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:579)
    at  at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.submit(ScheduledThreadPoolExecutor.java:731)
    at  at net.logstash.logback.appender.AbstractLogstashTcpSocketAppender.scheduleReaderCallable(AbstractLogstashTcpSocketAppender.java:1109)
    at  at net.logstash.logback.appender.AbstractLogstashTcpSocketAppender$TcpSendingEventHandler.openSocket(AbstractLogstashTcpSocketAppender.java:799)
    at  at net.logstash.logback.appender.AbstractLogstashTcpSocketAppender$TcpSendingEventHandler.onStart(AbstractLogstashTcpSocketAppender.java:691)
    at  at net.logstash.logback.appender.AsyncDisruptorAppender$EventClearingEventHandler.onStart(AsyncDisruptorAppender.java:382)
    at  at net.logstash.logback.encoder.com.lmax.disruptor.BatchEventProcessor.notifyStart(BatchEventProcessor.java:224)
    at  at net.logstash.logback.encoder.com.lmax.disruptor.BatchEventProcessor.run(BatchEventProcessor.java:120)
    at  at java.base/java.lang.Thread.run(Thread.java:1583)

I am having those dependencies:

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-to-slf4j</artifactId>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
        </dependency>
        <dependency>
            <groupId>net.logstash.logback</groupId>
            <artifactId>logstash-logback-encoder</artifactId>
            <version>7.4</version>
        </dependency>

And configured my logback file as per the tutorial, like this:

<configuration>
    <appender name="JSON_TCP" class="net.logstash.logback.appender.LogstashTcpSocketAppender">
        <destination>intake.logs.datadoghq.com:10514</destination>
        <keepAliveDuration>20 seconds</keepAliveDuration>
        <encoder class="net.logstash.logback.encoder.LogstashEncoder">
            <prefix class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
                <layout class="ch.qos.logback.classic.PatternLayout">
                    <pattern>5aa43880a6a7aa59a48286a5a2a6a548 %mdc</pattern>
                </layout>
            </prefix>
        </encoder>
    </appender>

    <root level="DEBUG">
        <appender-ref ref="JSON_TCP" />
    </root>
</configuration>

How to resolve this connection refused issue?