Connection refused: localhost/127.0.0.1 when I use spring boot and lettuce in a RaspberryPi

Question

I am trying to make a personal server by using RaspberryPI 4. I installed Ubuntu in it.

This is my code which is used for testing Redis.

@Bean
public RedisConnectionFactory redisConnectionFactory() {
    return LettuceConnectionFactory(redisHost, redisPort);
}

When I run it in my window desktop and Linux laptop, it does not make any problem.

But in the case of my raspberryPI, the below happen.

Caused by: io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: localhost/127.0.0.1:6389
Caused by: java.net.ConnectException: Connection refused
        at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
        at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:714)
        at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:330)
        at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334)
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:702)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
        at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
        at java.lang.Thread.run(Thread.java:748)

Do anyone know how to solve it?