Problems with CLX

Being new to CLX, I was looking at the CLX documentation
<http://tinyurl.com/yjnvkz>, specifically the small example program at
the beginning.  I can't get it to work for me.  In particular, I can't
seem to get open-display to work for me.  Here is the error I'm
getting.

Connection failure to X11.0 server 127.0.0.1 display 0: No protocol specified

   [Condition of type XLIB:CONNECTION-FAILURE]

Because the error string mentioned that no protocol was specified, I
tried to see if I could do something with the keyword argument.  I
also tried skimming through the code at ftp://ftp.franz.com/pub/clx/,
to see if I could discover the valid values of protocol, but I didn't
have much luck, especially as I don't know if I'm looking at the right
thing.

PG-USER> (xlib:open-display "127.0.0.1")
 0[6]: (XLIB:OPEN-DISPLAY "127.0.0.1")
   1[6]: (XLIB::OPEN-X-STREAM "127.0.0.1" 0 NIL)
   1[6]
; Fast loading from bundle code/acldns.fasl.
: returned
           #<MULTIVALENT stream socket connected from localhost/53972
             to localhost/6000 @ #x11adff22>
 0[6]: returned-by-throwing to tag -268441289: 0
; Evaluation aborted
PG-USER> (xlib:open-display "127.0.0.1" :protocol :tcp)
 0[6]: (XLIB:OPEN-DISPLAY "127.0.0.1" :PROTOCOL :TCP)
   1[6]: (XLIB::OPEN-X-STREAM "127.0.0.1" 0 :TCP)
   1[6]: returned
           #<MULTIVALENT stream socket connected from localhost/53973
             to localhost/6000 @ #x11b3e39a>
 0[6]: returned-by-throwing to tag -268441289: 0
; Evaluation aborted
PG-USER> (xlib:open-display "127.0.0.1" :protocol :duff)
 0[6]: (XLIB:OPEN-DISPLAY "127.0.0.1" :PROTOCOL :DUFF)
   1[6]: (XLIB::OPEN-X-STREAM "127.0.0.1" 0 :DUFF)
   1[6]: returned
           #<MULTIVALENT stream socket connected from localhost/53975
             to localhost/6000 @ #x11b596f2>
 0[6]: returned-by-throwing to tag -268441289: 0
; Evaluation aborted

Nothing I do with the protocol argument seems to make any difference
to the result at all.  Any help would be appreciated.  Here is my
system information:

PG-USER> (lisp-implementation-type)
"International Allegro CL Professional Edition"
PG-USER> (lisp-implementation-version)
"8.0 [Mac OS X] (Nov 11, 2006 22:53)"
PG-USER> (software-type)
"Apple Mac OS X 10.4"
PG-USER> (software-version)
"Darwin Damien-Kicks-Computer.local 8.8.0 Darwin Kernel Version 8.8.0: ..."