Kamran Karimi wrote:
> I have a benchmark program that uses connect() to create TCP/IP connctions
> between two Linux boxes as fast as it can. After a connection is open,
> some data is transferred, the socket is closed, the next socket is
> created, and so on.
>
> This works fine between slow machines. But when I run it on faster machines
> (where sockets are created and closed something like 250 times a second),
> after a while (about 3500 socket open/close operations) connect() fails
> with a "resource temporarily unavailable" error message. Other services
> like ftp stop working too.
>
> Is my program as fault here, or is this a kernel limitation?
AFAICT, it's somewhere between a kernel limitation and a TCP
limitation.
What I presume is happening is that whichever port number is chosen
for the client end will produce a socket which conflicts with one
which is in the TIME_WAIT state.
> Can I avoid this problem without having to limit the number of
> connections in my benchmark program?
On 2.2.*, you can increase the number of ephemeral ports available by
writing to /proc/sys/net/ipv4/ip_local_port range.
However, this will only make the problem harder to trigger.
Ultimately, if you make connections fast enough you will run into the
fact that TCP only uses 16-bit port numbers.
--
Glynn Clements <[EMAIL PROTECTED]>
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