I've added a new stack to revonline - UDP Repay (under alextweedly,
category programming)
It can be used to replay a stored log of UDP packets, such as you would
want to do for application testing and stress testing. It simply replays
a series of packets, keeping the original timing characteristics.
Although it can handle multiple interleaved streams of packets to
different ports, and can map them to new destination addresses and
ports, it can't do anything intelligent (or indeed anything at all) to
the streams themselves.
I will some day finish and upload the corresponding "UDP Recorder" stack
- but the limitations on how you can insert a UDP recorder stack into a
network context make it be of rather limited value. It's (generally)
much easier to add recording functions to your own app, and then have it
record a series of packets while in use. Then you can take the
resulting file of packets, and recreate it as a UDP stream, for testing
while the real data source is unavailable (or simply because you want a
repeatable set of test data).
Some sample functions that you could add to your stack are enclosed
below; usage should be fairly obvious
call "recorderStart pFilename" to start recording
call "recorderRecord pSock, pData" for every packet received (as near
to the original receipt of the packet as possible)
call "recorderFinish" when you're done
You can then use the UDP Replay stack to replay this file - with
controls for
- speed (%age of original)
- jitter (random variation of +- 20% of inter-packet delay)
- immediate start (often you'll set up the recorder, then have to go
off and get everything else started, so there will be a long delay
before the initial packet captured; this check box allows you to skip
this initial delay on replay.
Note - it doesn't yet allow you to induce mis-ordered packets ....
that's coming later, once I have researched current thinking about what
kind of misordering is likely.
-- ------ functions to include in your app ------------
-- initial recode in the file
-- 1-4 length of first record *including* the length and the separating
CR which is not part of the data recorder
-- 6-17 timestamp
-- <cr>
-- format of each record is
-- 1-4 length *including* the length and the separating CR which is
not part of the data recorder
-- 6-9 socket number
-- 11-22 timestamp
-- 24 - (length-1) actual data received / to be sent
-- <cr>
local lPorts, lStartTime, lPackets, lBytes, lFileName
on recorderStart pFileName
put pFileName into lFileName
put the milliseconds into lStartTime
open file lFileName for binary write
write format("%4d %12d", 18, lStartTime) & cr to file lFileName
put 0 into lPackets
put 0 into lBytes
end recorderStart
on recorderRecord pSock, pData
put format("%12d", milliseconds() - lStartTime) into tMsec
put 4 + 1 + 4 + 1 + 12 + 1 + len(pData)+1 into tLen
write format("%4d %4d %12d", tLen, pSock, tMsec) && pData &CR to
file lFileName
add 1 to lPackets
add len(pData) to lBytes
end recorderRecord
function recorderStatus
return the milliseconds - lStartTime, lPackets, lBytes
end recorderStatus
function recorderFinish
close file lFileName
return the milliseconds - lStartTime, lPackets, lBytes
end recorderFinish
--
Alex Tweedly http://www.tweedly.net
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