i had a similar problem when trying to install MySQL. a socket is what allows you to connect to a service (i.e., MySQL, Apache) running on your local machine.
after rtfm'img until the wee hours of the morning, i decided to completely remove the MySQL directory and untar it again. i started from scratch, and then when i tried to connect to MySQL, it worked! don't know whether or not i did things differently, but when i did a ls -a /tmp there was the beautiful little mysql socket in all it's glory.
but before you do anything drastic, try the command as root (i noticed your prompt wasn't su'd). if that doesn't work, start from square one, making sure to run all installation commands as root.
hope this helps.