(use unix-sockets)
(use posix)

(define-values (ip op ic oc) (unix-pair))
(process-fork (lambda ()
                (let ((p (current-process-id))
                      (r (read-line ic)))
                  (print "pid " p " read: " r)
                  (let ((w (number->string (+ 1 (string->number r)))))
                    (print "pid " p " write: " w)
                    (write-line w oc)
                    (flush-output oc)
                    (print (read-line ic))))))

(let ((p (current-process-id))
      (w (number->string (random 33))))
  (print "pid " p " write: " w)
  (write-line w op)
  (let ((r (read-line ip)))
    (print "pid " p " read: " r)
    (write-line "bye" op)
    (flush-output op)))

#|
Example output:

jim@aeryn ~/scheme/chicken-eggs4/unix-sockets/trunk$ csi -script socketpair-test.scm
pid 4411 write: 20
pid 4412 read: 20
pid 4412 write: 21
pid 4411 read: 21
bye
|#