TCP server with Spring boot reactor netty [duplicate] - spring-boot

Question

I would like to create a TCP server with Kotlin based on Spring reactive netty.
For this purpose I have the following demo project:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.8</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<kotlin.version>1.6.21</kotlin.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-reactor-netty</artifactId>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-reflect</artifactId>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-stdlib-jdk8</artifactId>
</dependency>
<dependency>
<groupId>io.projectreactor.kotlin</groupId>
<artifactId>reactor-kotlin-extensions</artifactId>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlinx</groupId>
<artifactId>kotlinx-coroutines-reactor</artifactId>
</dependency>
</dependencies>
<build>
<sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
<testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-plugin</artifactId>
<configuration>
<args>
<arg>-Xjsr305=strict</arg>
</args>
<compilerPlugins>
<plugin>spring</plugin>
</compilerPlugins>
</configuration>
<dependencies>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-allopen</artifactId>
<version>${kotlin.version}</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
</project>
package com.example.demo
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
#SpringBootApplication
class Main
fun main(args: Array<String>) {
runApplication<Main>(*args)
}
package com.example.demo
import kotlinx.coroutines.runBlocking
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.CommandLineRunner
import org.springframework.stereotype.Component
#Component
class DemoApplication : CommandLineRunner {
#Autowired
lateinit var server: Server
override fun run(vararg args: String?) {
runBlocking { server.run() }
}
}
package com.example.demo
import org.reactivestreams.Publisher
import org.springframework.stereotype.Service
import reactor.netty.DisposableServer
import reactor.netty.NettyInbound
import reactor.netty.NettyOutbound
import reactor.netty.tcp.TcpServer
#Service
class Server {
suspend fun run() {
val server: DisposableServer =
TcpServer.create().host("localhost").port(8080).handle(this::handler).bindNow()
server.onDispose().block()
}
fun handler(inbound: NettyInbound, outbound: NettyOutbound): Publisher<Void> {
val e = inbound.receive().retain()
return outbound.send(e)
// here, I would like to perform some operation on the incoming messages and writing their response using coroutine syntax without mono and flux
}
}
What I would like, is to be able to use the Kotlin coroutine syntax (with suspend function) to process the incoming message and produce the response, but for the moment I am stuck with the reactive functional syntax. How to pass from one world to another?
Would it be easier to use Netty without reactive project?