survey

#! /usr/bin/env scheme-script
; -*- mode: scheme -*-

; Getting Started with 'nanomsg'
; Survey
; from https://github.com/dysinger/nanomsg-examples#survey
#!chezscheme

(import (nanomsg) (chezscheme))

(nanomsg-library-init)

(define server-name "server")
(define client-name "client")
(define date-name "DATE")

(define date date-and-time)

(define (sleep-s sec)
  (sleep (make-time 'time-duration 0 sec)))

(define (server url)
  (define sock #f)
  (define eid #f)
  (dynamic-wind 
      (lambda ()
	(set! sock (nn-socket AF_SP NN_SURVEYOR)))
      (lambda ()
	(set! eid (nn-bind sock url))
	(sleep-s 1)
	
	(printf "SERVER: SENDING DATE SURVEY REQUEST~n")
	(nn-send sock (string->utf8 date-name) 0)
	(let loop ()
	  (let* ([buf (box #t)]
		 [bytes (guard (x [(= (nn-errno) ETIMEDOUT) #f])
			       (nn-recv sock buf NN_MSG 0))])
	    (unless bytes
		    (printf "SERVER: RECEIVED ~d SURVEY RESPONSE~n" 
			    (utf8->string (unbox buf)))
		    (loop)))))
      (lambda ()
	(if eid (nn-shutdown sock eid)))))

(define (client url name)
  (define sock #f)
  (define eid #f)
  (dynamic-wind 
      (lambda ()
	(set! sock (nn-socket AF_SP NN_RESPONDENT)))
      (lambda ()
	(set! eid (nn-connect sock url))
	(let loop ()
	  (let* ([buf (box #t)]
		 [bytes (guard (x [else #f])
			       (nn-recv sock buf NN_MSG 0))])
	    (when bytes
		  (printf "CLIENT (~d): RECEIVED ~d SURVEY REQUEST~n" 
			  name (utf8->string (unbox buf)))
		  (printf "CLIENT (~d): SENDING DATE SURVEY RESPONSE~n" 
			  name)
		  (nn-send sock (string->utf8 (date)) 0)
		  (loop)))))
      (lambda ()
	(if eid (nn-shutdown sock eid)))))

(define argv (command-line-arguments))
(define argc (length argv))

(cond
 [(and (> argc 1) (string=? server-name (car argv)))
  (server (cadr argv))]
 [(and (> argc 2) (string=? client-name (car argv)))
  (client (cadr argv) (caddr argv))]
 [else
  (printf "Usage: survey ~d|~d <URL> <ARG> ...'~n" server-name client-name)])


#!eof

./survey server ipc:///tmp/survey.ipc & server=$!
./survey client ipc:///tmp/survey.ipc client0 & client0=$!
./survey client ipc:///tmp/survey.ipc client1 & client1=$!
./survey client ipc:///tmp/survey.ipc client2 & client2=$!
sleep 3
kill $server $client0 $client1 $client2