Bizarre behavior of emacsclient on OS/X

[Bruce Korb]

> $ getconf DARWIN_USER_TEMP_DIR
> /var/folders/22/_6n21qmj3rgfqtrqy2nd81d8898tm8/T/
> $ id -u
> 278162056
> $ f=$(getconf DARWIN_USER_TEMP_DIR)/emacs$(id -u)/emacs
> $ file $f
> /var/folders/22/_6n21qmj3rgfqtrqy2nd81d8898tm8/T//emacs278162056/emacs: socket
> $ emacsclient -n -s $f myfile
> $

I'm writing because:

1. emacsclient does not default to the same temp directory, and
2. when I force it to use the correct temp directory, the emacs daemon (server)
   does *not* open "myfile".

How do I chase down the cause?