On Aug 10, 2011, at 8:33 AM, Gregory Lypny wrote:
> Hello everyone,
>
> I’m building a standalone for my students. It will allow them to upload
> quizzes and small assignments to my Mac via FTP as well as participate in
> various experiments and surveys. I have a few Internet-related questions
> that I hoping someone can answer.
>
> Is there a handler I can include in the stack that would allow it to detect
> whether the user is connected to the Internet? That would allow me to give
> them the option of working offline.
>
> How can I get the current date and time from either a time server or my
> remote Mac? I need to timestamp student submissions and want the time coming
> from one source, not their own machines.
>
> What is the best way to catch common FTP errors, such as a file not existing,
> so that I can relay a message back to the users?
>
>
>
> Much obliged,
>
> Gregory
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Hi Gregory,
> What is the best way to catch common FTP errors, such as a file not existing,
> so that I can relay a message back to the users?
After doing an FTP transaction, put the result into a variable. If the
variable is empty then the transaction was successful. If there was an error,
the variable will contain the exact error that occurred. You can then return
that error to the user.
> How can I get the current date and time from either a time server or my
> remote Mac? I need to timestamp student submissions and want the time coming
> from one source, not their own machines.
Timestamping from the perspective the client is very easy. Doing it from a
central clock is a bit more complex. Two solutions I can think of would be to
pull the time from the internet or running a CGI on the server and pulling it
from the server. If the Macs are set to keep their timing in sync with the
internet then using the local time on each system should be accurate enough
though.
Here is how you can check for the internet. The csDebugOutput lines can be
removed. They are used to log the function. I have included that handler in
the event you want to log it as well. This function scales nicely for users
that have higher latency connections. Users that have lower latency
connections will not be penalized and will normally return a true or false
value within 20 milliseconds. I have seen affordable dsl connections take as
much as 1500 milliseconds. Some international users may need as much as 3000
milliseconds on dial up connections. The function allows for up to 6000
milliseconds. This value can be modified as needed. The tSiteToCheck variable
can be set to any website. We used to use Google, but found testing against
our own sever served us in two ways. We could see if the client would have
issues resolving a connection to our server as well as testing for the ability
to communicate with the Internet.
local lInternetFirstCheck, lInternetFirstCheckTiming
function checkInternetStatus
--INITIALIZE VARIABLES
put 6000 into tFallbackTime
put "www.canelasoftware.com" into tSiteToCheck
put false into lInternetFirstCheck
csDebugOutput ("Starting checkInternetStatus...")
put hostNameToAddress(tSiteToCheck,"checkInternetStatus_Callback") into
tThrowAway
--GIVE SYSTEM TIME TO RUN THE hostNameToAddress FUNCTION
put the milliseconds into lInternetFirstCheckTiming --GATHER TIMING FOR
ACCURATE LOGGING
repeat until lInternetFirstCheck is true
wait 1 milliseconds with messages
if the milliseconds - lInternetFirstCheckTiming > tFallbackTime
then exit repeat
end repeat
--lInternetFirstCheck: true = DEFINITELY NOT CONNECTED TO ROUTER WITH NO
WAN
--lInternetFirstCheck: false = PROBABLY CONNECTED TO ROUTER WITH NO WAN
(OR WE HAVE POOR LATENCY)
--hostNameToAddress DID NOT RUN AND THUS RETURN NO INTERNET
--PROBABLY CONNECTED TO ROUTER WITH NO WAN (OR WE HAVE POOR LATENCY)
if lInternetFirstCheck is false then
csDebugOutput ("First internet check failed after:" && the
milliseconds - lInternetFirstCheckTiming & "ms")
csDebugOutput ("Probably connected to a router with no WAN (or we
have poor latency).")
return false
end if
--CHECK IF THE ROUTER HAS A VALID INTERNET CONNECTION
put hostNameToAddress(tSiteToCheck) into tInternetSecondCheck
--WE HAVE A VALID INTERNET CONNECTION
set the itemdel to "."
if item 2 of tInternetSecondCheck is a number then
csDebugOutput ("Second internet check passed after:" && the
milliseconds - lInternetFirstCheckTiming & "ms")
return true
end if
--WE ARE NOT CONNECTED TO A VALID INTERNET CONNECTION
csDebugOutput ("Second check failed after:" && the milliseconds -
lInternetFirstCheckTiming & "ms")
return false
end checkInternetStatus
on checkInternetStatus_Callback pParam1
csDebugOutput ("First internet check passed after:" && the milliseconds -
lInternetFirstCheckTiming & "ms")
put true into lInternetFirstCheck
end checkInternetStatus_Callback
command csDebugOutput pMessage
global gDebugModeOn
--BUILD LOG URL
if the platform is "Win32" then put ("file:" & (specialFolderPath(26) &
slash & kDebugLog)) into tLogURL
if the platform is "MacOS" then put ("file:" &
(specialFolderPath("preferences") & slash & kDebugLog)) into tLogURL
if tLogURL is empty then exit csDebugOutput
--CREATE TIMESTAMP
put (the long date && the long time && ": ") into tTimestamp
if gDebugModeOn is true then
if char 5 of pMessage = "#" then put (lf & lf & lf) before pMessage
--PREPEND MAJOR SECTIONS WITH LF*3
put 0 into x
repeat (the num of chars of pMessage)
add 1 to x
put char x of pMessage into tChar
if tChar is not lf and tChar is not cr and tChar is not crlf
then
put tTimestamp before char x of pMessage --PUT THE
TIMESTAMP AFTER THE SPACES, AND BEFORE THE CONTENT
exit repeat
end if
end repeat
put (pMessage & cr) after URL tLogURL --WRITE TO THE LOG
end if
end csDebugOutput
Best regards,
Mark Talluto
http://www.canelasoftware.com
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