Comment #5 on issue 158 by eric.d.lambert: Single packet DoS on UDP channel http://code.google.com/p/memcached/issues/detail?id=158
I think i have somewhat of an idea as to what is happening. The UDP connections behave a little bit different than TCP. At start up, the server creates a UDP "connection handler" for each thread in the server (as controlled by the -t option). By default there are 4 threads so there will be 4 UDP "connection handlers".
What appears to be happening is that the message you are sending is not a valid/wellformed message which causes the server to close the "connection handler" in such a way that it can not be used again. So in a default scenario with the server running 4 threads, the first time you run your test one connect handler is closed leaving three left, the second run closes a second handler leaving two left and so on. If you start the server with only one thread (-t 1) you should hit the issue on the first run.
I dont have a root cause yet, but the issue does appear to be related to how the server clears up the connection handler when it encounters a problem. Will let you know when I've figured this out
