"Failed to connect to connect to FTP server" issue (Wordpress)

I set up a Wordpress installation on my web server. As soon as I tried to install a new theme/plugin, I got the message "Failed to connect to FTP server mydomain.com:21". I was certain that the address and login credentials where correct since I could connect to my FTP server with an FTP client (Filezilla).

I proceeded to set my wp-content folder's permissions to 755, as well as it's contents with:

chmod -R 755 /var/www/mywordpressfolder/wp-content/

I then changed ownership of the wp-content folder and its contents to the www-data user (apache user/group).

chown -R www-data /var/www/mywordpressfolder/wp-content/

This solved my issue. Needless to say, change mywordpressfolder with where your wordpress installation is. If your installation is not in a folder just use /var/www/wp-content/. If you get a "Permission denied/Operation not permitted" message, you probably omitted using "sudo" in front of the command.