net-sntp-testing.html
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>The SNTP package contains a simple test program. Testing an SNTP
client is not easy, so the test program should be considered as more a
proof of concept. It shows that an NTP packet has been received,
and is accurate to within a few days. </P
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>The test program starts the network interfaces using the standard
call. It then starts the SNTP thread. A loop is then entered printing
the current system time every second for two minutes. When the client
receives an NTP packet the time will jump from 1970 to hopefully the
present day. Once the two minutes have expired, two simple tests are
made. If the time is still less than 5 minutes since 00:00:00
01/01/1970 the test fails. This indicates no NTP messages have
been received. Check that the server is actually sending packet, using
the correct port (123), correct IPv6 multicast address, and at a
sufficiently frequent rate that the
target has a chance to receive a message within the 2 minute
interval. If all this is correct, assume the target is broken. </P
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>The second test is that the current system time is compared with the
build time as reported by the CPP macro __DATE__. If the build date is
in the future relative to the system time, the test fails. If the
build date is more than 90 days in the past relative to the system
time the test also fails. If such failures are seen, use walk-clock
time to verify the time printed during the test. If this seems correct
check the build date for the test. This is printed at startup. If all
else fails check that the computer used to build the test has the
correct time. </P
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>If SNTP unicast mode is enabled, the above tests are run twice. The
first time, the SNTP client is configured with NTP server addresses
from DHCP. The second time, unicast mode is disabled and only
multicasts are listened for. Note that the unicast test is partially
bogus in the sense that any multicast packet received will also make
the unicast test pass. To reduce the chance of this happening the
test will wait for a sorter time for replies. This is not ideal, but
it is the best that can be done with an automated test.</P
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