42 lines
1.7 KiB
Racket
42 lines
1.7 KiB
Racket
;;; SPDX-License-Identifier: LGPL-3.0-or-later
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;;; SPDX-FileCopyrightText: Copyright © 2010-2021 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
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#lang syndicate
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(require/activate syndicate/drivers/timer)
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(require/activate syndicate/drivers/udp)
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(require racket/random file/sha1)
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;; IANA offers guidelines for choosing multicast addresses [1].
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;;
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;; Reasonable candidates for local experimentation include:
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;; - 224.0.1.20, "any private experiment"
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;; - 233.252.0.0 - 233.252.0.255, "MCAST-TEST-NET", for examples and documentation (only)
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;;
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;; For production and semi-production use, registering an address may
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;; be an option; failing that, the Administratively Scoped Block
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;; (239/8; see RFC 2365) may be used:
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;; - 239.255.0.0 - 239.255.255.255, "IPv4 Local Scope"
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;; - 239.192.0.0 - 239.195.255.255, "Organization Local Scope"
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;;
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;; [1] http://www.iana.org/assignments/multicast-addresses/
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(define group-address "233.252.0.101") ;; falls within MCAST-TEST-NET
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(define group-port 5999) ;; make sure your firewall is open to UDP on this port
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(spawn (define me (bytes->hex-string (crypto-random-bytes 8)))
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(define h (udp-listener group-port))
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(during h
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(assert (udp-multicast-group-member h group-address #f))
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(assert (udp-multicast-loopback h #t))
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(field [deadline (current-inexact-milliseconds)])
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(on (asserted (later-than (deadline)))
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(send! (udp-packet h
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(udp-remote-address group-address group-port)
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(string->bytes/utf-8 (format "~a ~a" me (deadline)))))
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(deadline (+ (deadline) 1000)))
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(on (message (udp-packet $source h $body))
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(printf "~a: ~a\n" source body))))
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