[racket] Help with sockets.

From: Danny Yoo (dyoo at hashcollision.org)
Date: Tue Apr 22 16:46:53 EDT 2014

One thing you might need to think about is buffering.  Here's another
example of a Racket server that doubles up the bytes it reads:

#lang racket
(define listener (tcp-listen 12346 4 #t))
(let doubler-server ()
  (define-values (in out) (tcp-accept listener))
  (thread (λ () (let loop ()
                  (define b (read-byte in))
                    [(eof-object? b)
                     (close-output-port out)]
                     (write-byte b out)
                     (write-byte b out)
                     (flush-output out)

The Python client can stay the same.

The use of flush-output is there because we want to flush the buffer
and send the buffered bytes over the network.

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