Why does ServerSocket stop working after some time?

Hi to all.

I have a following problem:

I wrote a multithread application that uses sockets ( TCP ), and use it to transfer some objects between computers in VPN.

It all works just fine, except that sometimes my server socket ( implemented as a separate Thread ) just stops working, and other computers cannot connect to it...?

I didn't specify setSOTimeout(), and did all Exception catch-ing in the thread.

Today, I had some >50000 connections in about 5 hours, and than it just stopped! My server socket stopped accepting any connections...
I restarted my application, and everything worked again properly...

Does anybody know why is this happening?
Please, any suggestion is appreciated....
Thank you.

Don't catch Exception,catch the actual exceptions. What were the exceptions?

Sounds like someone DOSed you.

Rusty Shackleford wrote:Don't catch Exception,catch the actual exceptions. What were the exceptions?

Sounds like someone DOSed you.

Unfortunately - no Exception was reported...
(I handle only the IOException because timeout was not previously set, there is no SecurityManager and no channel was associated with this socket )

Maybe I shoul use setSOTimeout()?

What does

someone DOSed you

means?

Again, ANY idea is appreciated...

Are you closing the sockets in finally blocks when done?

DOS = Denial Of Service.

Moojid Hamid wrote:Are you closing the sockets in finally blocks when done?

DOS = Denial Of Service.

Yes I do.

And how do I prevent DOS attacks? Do you have any suggestion?

with 50000 connections, you need to check your process resource utilization when the server hang:
1. number of threads
2. memory foot print
3. cpu usage

you can use jconsole to attach to your process, or issue a sigquit to your UNIX process to see the stack trace.

Also, i would suggest you load balance the traffic to more than one process for better scalability