[plt-scheme] TCP example not working

The example below is given in the guide hangs around  (read-line s-in) .

(define server (tcp-listen 12345))
(define-values (c-in c-out) (tcp-connect "localhost" 12345))
(define-values (s-in s-out) (tcp-accept server))
(display "hello\n" c-out)
(read-line s-in)
(close-output-port c-out)
(read-line s-in)


My drscheme environment is:
Welcome to DrScheme, version 4.1 [3m].
Language: Pretty Big.