...
    // Cleanup directories
    clean: {
      server: '<%= config.server %>'
    },
  ...
  
    /* Run server

   - clean server directory
   - copy sources into server directory
   the remaining tasks use the files from the server directory
   - start grunt server
   - start watching project source files
   */
  grunt.registerTask('server', [
    'clean:server',
    'copy:server',
    'connect',
    'watch'
  ]);