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Java Forum / General / October 2006Dropped Sockets?
Hi, I've built a client-server program that is designed to test server load on a brand new Mac Pro machine of ours. There are two programs: a server and a client generator. The server sits idly waiting for connections (done in SSL), and the client just generates a ton of clients at evenly spaced intervals (like every 100 milliseconds or so). For some reason, on the Mac machine, I get random "SocketConnection: Socket Closed" errors when I try to do write operations. I can not trace down any rhyme or reason as to why this is happening and nearly went crazy trying to debug my code... and then I tried the same code on my Dell Laptop running Ubuntu... worked like a charm! Why would I be losing sockets like this? Josh <>< > Hi, I've built a client-server program that is designed to test server > load on a brand new Mac Pro machine of ours. [quoted text clipped - 11 lines] > > Why would I be losing sockets like this? The first thought that comes to mind is differing socket implementations on mac and linux, the same goes for the jvm. You should try to isolate what causes the problem. First you should try to figure out if its an os problem or a jvm/language problem. - can you create a similar program on the mac in a different language, preferably one using the kernel api directly, such as c/c++. If the problem persists its an os problem, if not, its a jvm problem. - is there a different jvm you could try on the mac. if the problem persists it its probably a language problem (such as a bad design/implementation decision or perhaps a faulty jvm conformance test.). You could also try to reduce the number of running clients/open sockets on the mac, to see if the problem persists. An that way try to find a way around the problem tom Any hints would be appreciated at this point! Sometimes the very first connection is dropped... sometimes no connections are dropped and sometimes all of them work. It is entirely random! I have also done a look at netstat on the Mac OS X machine after running the test once with only 10 clients... where 1 of the clients bombed after trying to do a write() operation and gave a SocketException: Socket closed Error. Netstat did indeed show that only 9 of the connections existed (and they were all healthy, as well). It just seems so unusual... Josh <>< > Any hints would be appreciated at this point! > [quoted text clipped - 13 lines] > > Josh <>< what is the network topology? are there firewalls between/on the machines? any hardware routers that could be dodgy? if possible try removing them temporarily. perhaps by connecting the two machines by a crossover cable. Can you run a ping test from one machine to the other during application use and see if there are any issues? Tim Ok, here's some more info: No firewalls whatsoever. The problem is the client generator... ONLY when it runs on Mac OS X. Could this be a problem with the way Mac OS X implements SSL? This doesn't make ANY sense to me now... I'm trying to rip apart my code and debug things to see where the problem is occurring, but I'm having quite a time doing it. The error(s) (socket closed, broken pipe etc.) always occur on the server app (regardless of the type of machine) and the client doesn't EVER report an error... so I had assumed it was the server code, but apparently it's not... since the errors only show up on the server when the client is run on Mac OS X. Can you read too quickly from a socket after an SSL connection? Need any help! Josh <>< > Ok, here's some more info: > [quoted text clipped - 13 lines] > > Can you read too quickly from a socket after an SSL connection? Does other java code, f.ex. created by another person/project, using ssl work as expected, if so then the problem is your code, perhaps a portability problem. If not it might be the ssl library or as I stated earlier, the jvm. If is your code that is the problem, you need to provide more details about the code f.ex. some code samples with error messages etc. Or you could pick up a book, or something, that you can use to help verify the code. tom Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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