read-line returns eof when the port is closed, which is completely
different from sending byte 04 (or any other byte or sequence of bytes)
over the port.
;; set up {client,server}-{in,out} ports
(write-byte 4 client-out)
(flush-output client-out)
(read-byte server-in) ;; => 4
(close-output-port client-out)
(read-byte server-in) ;; => #<eof>
If you want to consider U+0004 a line-breaking character, you'll have to
write the code that does that yourself. Using regexp-match on the input
port might be the most convenient way.
Ryan
On 02/22/2017 07:49 PM, Jordan Johnson wrote:
Hi all,
Quick question: Given a listener and input port defined thus:
(define listener (tcp-listen port))
(define-values (in out) (tcp-accept listener))
while reading lines of text, what’s the correct way to detect an EOT (^D or
U+0004) character?
This “obvious” solution does not work:
(for ([line (in-lines in)])
#:break (eof-object? line)
...)
Neither does this (which I wouldn’t expect to work, after the above didn’t):
(let loop ([val (read-line in)])
(unless (eof-object? val)
...))
I’ve determined that the eof-object? calls are never producing #t, even if ^D
is the very first thing the client sends. I’m thinking there’s something
super-basic that I’m forgetting.
What am I missing here?
Thanks,
Jordan
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