Ktor error: Neither port nor sslPort specified

So, I've read numerous answers on how to resolve this error, but it doesn't seem to apply to my situation.

This is a ktor application, built with maven.

I'm getting the error: Exception in thread "main" java.lang.IllegalArgumentException: Neither port nor sslPort specified. Use command line options -port/-sslPort or configure connectors in application.conf

First of all, my application runs fine in IntelliJ Ultimate, but fails when I try to run the fatjar on the commandline like this: java -jar target/myApp-jar-with-dependencies.jar

The crux of the matter seems to be that I'm having my configuration in an application.yaml file.

I've included this dependency:

    <dependency>
        <groupId>io.ktor</groupId>
        <artifactId>ktor-server-config-yaml-jvm</artifactId>
        <version>${ktor_version}</version>
    </dependency>

My application structure looks like this:

When I create an application.conf in the same folder it works fine, which indicates that it just does not expect a yaml configuration file, even when I've included the ktor yaml dependency.

Lastly, my maven build segment looks like this:

 <build>
    <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
    <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
    <resources>
        <resource>
            <directory>${project.basedir}/src/main/resources</directory>
        </resource>
    </resources>

    <plugins>
        <plugin>
            <artifactId>kotlin-maven-plugin</artifactId>
            <groupId>org.jetbrains.kotlin</groupId>
            <version>${kotlin_version}</version>
            <configuration>
                <jvmTarget>17</jvmTarget>
                <compilerPlugins>
                    <plugin>kotlinx-serialization</plugin>
                </compilerPlugins>
            </configuration>
            <executions>
                <execution>
                    <id>compile</id>
                    <phase>compile</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
                <execution>
                    <id>test-compile</id>
                    <phase>test-compile</phase>
                    <goals>
                        <goal>test-compile</goal>
                    </goals>
                </execution>
            </executions>
            <dependencies>
                <dependency>
                    <groupId>org.jetbrains.kotlin</groupId>
                    <artifactId>kotlin-maven-serialization</artifactId>
                    <version>${kotlin_version}</version>
                </dependency>
            </dependencies>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.2.1</version>
            <executions>
                <execution>
                    <goals>
                        <goal>java</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <mainClass>${main.class}</mainClass>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.6</version>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <mainClass>${main.class}</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <id>assemble-all</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Any help would be appreciated.

Ktor uses the ServiceLoader to load all the available config loaders and then tries to load the default configuration with each. The HoconConfigLoader is defined in the ktor-server-core-jvm module, and the YamlConfigLoader is defined in the ktor-server-config-yaml-jvm module. As far as I understand, the assembly Maven plugin takes the META-INF/services/io.ktor.server.config.ConfigLoader file of the first package containing that file and packages it in the result JAR.

Since the ktor-server-core-jvm module goes first in the dependencies block in the pom.xml, the plugin packages only a definition of the HoconConfigLoader and ignores the one for YAML. As a result, the application only tries to load the application.conf file, which doesn't exist.

To solve the problem, switch the order of the dependencies in the pom.xml file:

<dependencies>
    <dependency> <!-- To be able to use yaml as server configuration -->
        <groupId>io.ktor</groupId>
        <artifactId>ktor-server-config-yaml-jvm</artifactId>
        <version>${ktor_version}</version>
    </dependency>
    <!-- Ktor -->
    <dependency>
        <groupId>io.ktor</groupId>
        <artifactId>ktor-server-core-jvm</artifactId>
        <version>${ktor_version}</version>
    </dependency>
<!-- ... -->
<dependencies>