Kurento groupcall - websocket connection failed

Question

I'm trying to set up groupcall in my webapp using kurento tutial for group calls. In tutorial, server.port config in application.properties is inserted via ${demo.port} from pom.xml. In my app, when i tried using it, I got error stating that I can't use string so I've replaced {demo.port} in app.prop with 8443 (intended port). Since then i can't connect to websocket and i get error in browser (in screen)

my code: pom.xml:

<?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>3.2.2</version>
<!--        <relativePath/> &lt;!&ndash; lookup parent from repository &ndash;&gt;-->
    </parent>
    <groupId>pl.Held</groupId>
    <artifactId>Held</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Held</name>
    <description>Held</description>

    <properties>
        <demo.port>8443</demo.port>
        <java.version>17</java.version>
        <start-class>pl.held.HeldApplication</start-class>
    </properties>


    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-websocket</artifactId>
        </dependency>

        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/jakarta.servlet.jsp.jstl/jakarta.servlet.jsp.jstl-api -->
        <dependency>
            <groupId>jakarta.servlet.jsp.jstl</groupId>
            <artifactId>jakarta.servlet.jsp.jstl-api</artifactId>
            <version>3.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>jakarta.servlet.jsp.jstl</artifactId>
            <version>3.0.1</version>
        </dependency>


        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
        </dependency>


        <!-- WebJars -->
        <!-- https://mvnrepository.com/artifact/org.webjars/webjars-locator -->
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>webjars-locator</artifactId>
            <version>0.50</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.webjars.bower/jquery -->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>jquery</artifactId>
            <version>3.7.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.webjars.bower/bootstrap -->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>bootstrap</artifactId>
            <version>5.3.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.webjars.bower/demo-console -->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>demo-console</artifactId>
            <version>1.5.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.webjars.bower/ekko-lightbox -->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>ekko-lightbox</artifactId>
            <version>5.2.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.webjars.bower/webrtc-adapter -->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>webrtc-adapter</artifactId>
            <version>7.4.0</version>
        </dependency>


        <!-- Kurento -->
        <!-- https://mvnrepository.com/artifact/org.kurento/kurento-client -->
        <dependency>
            <groupId>org.kurento</groupId>
            <artifactId>kurento-client</artifactId>
            <version>6.18.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.kurento/kurento-utils-js -->
        <dependency>
            <groupId>org.kurento</groupId>
            <artifactId>kurento-utils-js</artifactId>
            <version>6.18.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-assembly-plugin -->
        <dependency>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>3.6.0</version>
        </dependency>




    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>

        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
                <includes>
                    <include>application.properties</include>
                    <include>banner.txt</include>
                </includes>
            </resource>
        </resources>
    </build>

    <profiles>
        <profile>
            <id>default</id>
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-assembly-plugin</artifactId>
                        <configuration>
                            <descriptors>
                                <descriptor>src/assembly/bin.xml</descriptor>
                            </descriptors>
                            <finalName>${project.artifactId}-${project.version}</finalName>
                            <appendAssemblyId>false</appendAssemblyId>
                        </configuration>
                        <executions>
                            <execution>
                                <phase>package</phase>
                                <goals>
                                    <goal>single</goal>
                                </goals>
                            </execution>
                        </executions>
                    </plugin>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-antrun-plugin</artifactId>
                        <executions>
                            <execution>
                                <phase>package</phase>
                                <configuration>
                                    <tasks>
                                        <copy file="${project.build.directory}/target/${project.artifactId}-${project.version}-bin.zip" tofile="${project.build.directory}/target/${project.artifactId}-${project.version}.zip"/>
                                    </tasks>
                                </configuration>
                            </execution>
                        </executions>
                    </plugin>
                </plugins>
            </build>
        </profile>
        <profile>
            <id>no-assembly</id>
        </profile>
    </profiles>
</project>

Application file:

package pl.held;

import org.kurento.client.KurentoClient;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
import org.springframework.web.socket.server.standard.ServletServerContainerFactoryBean;
import pl.held.groupcall.CallHandler;
//import pl.held.groupcall.GroupCallApp;
import pl.held.groupcall.RoomManager;
import pl.held.groupcall.UserRegistry;
@SpringBootApplication
@EnableWebSocket
public class HeldApplication implements WebSocketConfigurer {



    @Bean
    public UserRegistry registry() {
        return new UserRegistry();
    }

    @Bean
    public RoomManager roomManager() {
        return new RoomManager();
    }

    @Bean
    public CallHandler groupCallHandler() {
        return new CallHandler();
    }

    @Bean
    public KurentoClient kurentoClient() {
        return KurentoClient.create();
    }

    @Bean
    public ServletServerContainerFactoryBean createServletServerContainerFactoryBean() {
        ServletServerContainerFactoryBean container = new ServletServerContainerFactoryBean();
        container.setMaxTextMessageBufferSize(32768);
        return container;
    }

    public static void main(String[] args) throws Exception{
        SpringApplication.run(HeldApplication.class, args);
    }
//    public static void main(String[] args) throws Exception {
//        SpringApplication.run(GroupCallApp.class, args);
//    }

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(groupCallHandler(), "/groupcall");

    }

}

application.properties:

spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:mysql://**********
spring.datasource.username=**********
spring.datasource.password=**********
spring.mvc.view.prefix=/WEB-INF/views/
spring.mvc.view.suffix=.jsp

# ===================================================================
# Spring Boot application properties
#
# For a list of common properties, check the Spring Boot docs:
# https://docs.spring.io/spring-boot/docs/current/reference/html/appendix-application-properties.html
# ===================================================================


# ----------------------------------------
# CORE PROPERTIES
# ----------------------------------------

# BANNER
banner.location=classpath:banner.txt

# LOGGING
logging.level.root=INFO
logging.level.org.apache=WARN
logging.level.org.springframework=WARN
logging.level.org.kurento=INFO
logging.level.org.kurento.tutorial=INFO

# OUTPUT
# Terminal color output; one of [ALWAYS, DETECT, NEVER]
spring.output.ansi.enabled=DETECT


# ----------------------------------------
# WEB PROPERTIES
# ----------------------------------------

# EMBEDDED SERVER CONFIGURATION
server.port=8443
server.ssl.key-store=classpath:keystore.jks
server.ssl.key-store-password=kurento
server.ssl.key-store-type=JKS
server.ssl.key-alias=kurento-selfsigned