Re: Using SNTP

["Nick Austin" <nick.w.austin@xxxxxxxxx>]

On Mon, Aug 11, 2008 at 9:10 AM, Neil Wrightson <neilw@xxxxxxx>
wrote:
> Hi Nick,
>
> Exactly my point.
>
> Approximately 60 A4 pages of data here, yet the author said he sent
one
> simple UDP packet and got one back with the current time in it.
> Surely somebody on this list has already shed the tears and blood over
these
> documents and would know what the packet might be.

OK.  You send one UDP packet to the time server. Every byte in that packet
is zero except the first.  The value of that first byte depends on the
the software
that the time server is running - get it wrong and the server ignores
the request.

To determine what values of the first byte are accepted you need to be
running
the full NTP protocol (since SNTP is designed for LANs where you have full
control over every machine in the network).  Using SNTP over the Internet
is
always going to be hit-and-miss.

If successful you get back 84 bytes which is in the format described by
RFC1361
in section titled "NTP Message Format".

Nick.

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