Failed to connect to FTP Server 127.0.0.1/:21

Tried to install a wordpress plugin on my local machine:

To perform the requested action, WordPress needs to access your web server. Please enter your FTP credentials to proceed. If you do not remember your credentials, you should contact your web host.

Hostname          127.0.0.1
FTP Username      macusername
FTP Password      macusernamepassword
Connection Type   Connection Type  FTP

When I click proceed, I get this:

Failed to connect to FTP Server 127.0.0.1/:21

Why doesn’t WordPress work with my FTP data?

Depending on your version of OS X, you will need to configure and run FTP and open a port in the firewall. It’s best if you google your OS X version – 10.6, 10.7, etc. – specifically and find the docs necessary to set up FTP and Sharing.

You also need to realize the security implications of opening up FTP to your local machine; someone port scanning your IP may be able to find your FTP port.

It’s often easiest – and the best for security – to simply download the plugin and move it into the plugins folder.