[plt-scheme] hamsup.ss problem with language selection

From: Wayne Iba (iba at westmont.edu)
Date: Thu Jun 1 20:14:25 EDT 2006

I'd like to use the hamsup teachpack for my intro class, but since v207, 
it has not worked.  The problem is with the (thread server-loop) in the 
following code.  (I removed the (thread server-loop) and essentially 
created a "one-time-listener" that worked fine within the Advanced student.)

(module hamsup mzscheme
  (require (lib "etc.ss"))
  (provide install-listener)
;; install-listener: number (sexpr -> void) -> void
  (define (install-listener port receiver)
    (local [(define listener (tcp-listen port))
            (define (server-loop)
              (local [(define-values (client->me me->client)
                        (tcp-accept listener))]
                  (close-output-port me->client)
                  (let ([the-value (read client->me)])
                      (close-input-port client->me)
                      (receiver the-value)
      (thread server-loop)))

If I run the teachpack within the (module...) language, I can create 
listeners just fine.  But within Advanced Student, I get the following 

 > (install-listener 9877 (lambda (x) (display x)))
(make-server-loophash-table-get: expects type <hash-table> as 1st 
argument, given: false; other arguments were: 'test-coverage-point45570

The "(make-server-loop" is in blue and the "hash-table-get: ..." is in 
red italics.  This happens in both v300 and v301 (on linux).  Note, 
after this call, the unix netstat utility indicates that we are 
listening on port 9877. Not surprisingly, messages to that port are not 
processed by the lambda function.

Your help is greatly appreciated in advance!
--Wayne Iba

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