modulename:
  core_address: 107.101.xx.yy
  core_port: 153759
  core_user: superuser
  core_pass: superpass

services:
    modulename.my_service:
        class: DrupalmodulenamegroupMyService

/**
 * @file
 * Contains DrupalmodulenamegroupMyService.
 */

namespace Drupalmodulenamegroup;

/**
 * MyService.
 */
class MyService{

  protected $demo_value;

  public function __construct() {
    $this->demo_value = 'hi there';
  }

  public function getDemoValue() {
    return $this->demo_value;
  }

}