77 lines
2.6 KiB
Scheme
77 lines
2.6 KiB
Scheme
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;;; nettime.scm -- obtain the time on remote machines
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;;
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;; $Id: nettime.scm,v 1.1 2002/06/08 15:05:24 sperber Exp $
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;;
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;; Please send suggestions and bug reports to <emarsden@mail.dotcom.fr>
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;;; Overview ========================================================
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;;
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;; Most Unix hosts provide a Daytime service which sends the current
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;; date and time as a human-readable character string. The daytime
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;; service is typically served on port 13 as both TCP and UDP.
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;;
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;; The Time protocol provides a site-independent, machine readable
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;; date and time. A "time" consists of the number of seconds since
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;; midnight on 1st January 1900. The Time service is typically served
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;; on port 37 as TCP and UDP. The idea is that you can confirm your
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;; system's idea of the time by polling several independent sites on
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;; the network.
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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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;; * rfc867 describes the Daytime protocol in all its glory
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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 (net-time host tcp/udp)
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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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tcp/udp
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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 (net-daytime host tcp/udp)
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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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tcp/udp
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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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;; 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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;; EOF
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