Hi,
Yes, this is on a lower level. It goes all the
way down to the BSD sockets network syscall
listen(2), and how connection-oriented transport
services (TCP) are implemented on top of a
connection-less network service (IP).
In Java this is seen in java.net.ServerSocket:
The backlog argument to the constructor determines
how many incoming connect requests that have not
yet been accepted will be enqueued. When this
limit is hit, the kernel TCP/IP implementation will
return a "connection refused" error to the caller.
This happens because clients send connection
requests at a higher rate than the server can do
the accept().
The problem really cannot be fixed, but by setting
the backlog higher it takes more for it to become
visible. Unfortunately a higher backlog value makes
the server more sensitive to some kinds of DoS
attacks. And IMHO the default backlog value of 50
in the ServerSocket is already quite high.
So I would recommend that nothing is done at
server side to fix this.
Rather, test clients that start a lot of connections
should ensure that they do not have too many
outstanding connection requests. A simple delay
between thread starts in the client also works, if
longer than the time it takes the server to do the
accept.
Best Regards,
Ole Husgaard.
"Rickard Öberg" wrote:
>
> Hi!
>
> Achim Demelt wrote:
> > Well, any concrete ideas for a solution? As I said, I wrote my own
> > RMISocketFactory and the container factory says that it created one of my
> > ServerSockets which should be able to handle 10000 incoming connections in
> > the backlog queue. Why do things still go wrong?
>
> To be honest, I don't know. It might be a problem on a lower level, e.g.
> the JVM or OS level. In that case there's not a lot you can do about it.
>
> Nevertheless, the scenario is probably not likely to occur in a
> production environment, so why bother with it?
>
> regards,
> Rickard
>
> --
> Rickard Öberg
>
> Email: [EMAIL PROTECTED]
>
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