112 lines
3.8 KiB
Scheme
112 lines
3.8 KiB
Scheme
;;; nettime.scm -- obtain the time on remote machines
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;;; This file is part of the Scheme Untergrund Networking package.
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;;; Copyright (c) 1998 by Eric Marsden
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;;; Copyright (c) 2003 by Mike Sperber <sperber@informatik.uni-tuebingen.de>
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;;; For copyright information, see the file COPYING which comes with
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;;; the distribution.
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;;; Related work ======================================================
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;;
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;; * Time.pm is a Perl module by Graham Barr
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;; * rfc868 describes the Time protocol
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;; http://www.ietf.org/rfc/rfc868.txt
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;; * rfc867 describes the Daytime protocol in all its glory
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;; http://www.ietf.org/rfc/rfc867.txt
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;; * for a genuinely useful protocol look at the Network Time Protocol
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;; defined in rfc1305, which allows for the synchronization of clocks
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;; on networked computers.
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;; args host protocol, where host may be an IP number or a fqdn. we
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;; subtract 70 years' worth of seconds at the end, since the time
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;; protocol returns the number of seconds since 1900, whereas Unix
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;; time is since 1970.
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(define (rfc868-time/tcp host)
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(let* ((hst-info (host-info host))
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(srvc-info (service-info "time" "tcp"))
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(sock (socket-connect protocol-family/internet
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socket-type/stream
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(host-info:name hst-info)
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(service-info:port srvc-info)))
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(result (read-integer (socket:inport sock))))
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(close-socket sock)
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(- result 2208988800)))
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(define (rfc868-time/udp host . maybe-timeout)
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(let* ((hst-info (host-info host))
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(srvc-info (service-info "time" "udp"))
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(timeout (if (pair? maybe-timeout)
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(car maybe-timeout)
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#f))
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(socket (create-socket protocol-family/internet socket-type/datagram)))
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(connect-socket socket
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(internet-address->socket-address
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(car (host-info:addresses hst-info))
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(service-info:port srvc-info)))
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(send-message socket "")
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(if (null? (select-ports timeout (socket:inport socket)))
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(begin
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(close-socket socket)
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#f)
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(with-fatal-error-handler*
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(lambda (result punt)
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;; we may see a "connection refused" error here
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#f)
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(lambda ()
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(let ((result (read-integer (socket:inport socket))))
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(close-socket socket)
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(- result 2208988800)))))))
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(define (rfc867-daytime/tcp host)
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(let* ((hst-info (host-info host))
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(srvc-info (service-info "daytime" "tcp"))
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(sock (socket-connect protocol-family/internet
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socket-type/stream
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(host-info:name hst-info)
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(service-info:port srvc-info)))
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(result (read-string 20 (socket:inport sock))))
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(close-socket sock)
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result))
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(define (rfc867-daytime/udp host . maybe-timeout)
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(let* ((hst-info (host-info host))
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(srvc-info (service-info "daytime" "udp"))
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(timeout (if (pair? maybe-timeout)
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(car maybe-timeout)
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#f))
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(socket (create-socket protocol-family/internet socket-type/datagram)))
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(connect-socket socket
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(internet-address->socket-address
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(car (host-info:addresses hst-info))
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(service-info:port srvc-info)))
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(send-message socket "")
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(if (null? (select-ports timeout (socket:inport socket)))
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(begin
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(close-socket socket)
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#f)
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(with-fatal-error-handler*
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(lambda (result punt)
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;; we may see a "connection refused" error here
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#f)
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(lambda ()
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(call-with-values
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(lambda () (receive-message socket 20))
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(lambda (result socket-address)
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(close-socket socket)
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result)))))))
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;; read 4 bytes from fd and build an integer from them
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(define (read-integer fd)
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(let loop ((accum 0)
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(remaining 4))
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(if (zero? remaining)
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accum
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(loop (+ (arithmetic-shift accum 8) (read-byte fd))
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(- remaining 1)))))
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;; what about EOF??
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(define (read-byte fd)
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(char->ascii (read-char fd)))
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