[erlang-questions] HTTP requests and the meaning of eaddrinuse

Johnny Billquist <>
Fri Jan 30 21:42:17 CET 2009


Sverker Eriksson wrote:
> Johnny Billquist wrote:
>> Sverker Eriksson wrote:
>>> Johnny Billquist wrote:
>>>> [...] you will most probably hit the limit of the number of open 
>>>> file descriptors long before you exhaust all the local port numbers. 
>>>> By default on on my mac, the max file descriptors is 256 (per 
>>>> process). There is also a limit on the total number of file 
>>>> descriptors in the OS. Nowhere near the theoretical limit of 65536 
>>>> ports in tcp. So that should give you enfile or emfile. 
>>> The internal TIME_WAIT state of the TCP protocol may cause exhaustion 
>>> of port numbers even though the file descriptor limit is much lower 
>>> than 65536. Use the netstat command tool to view lingering 
>>> connections in TIME_WAIT state.
>> True, if the connections aren't closed properly.
> Actually, kind of the opposite. The peer that actively closes the 
> connection by calling close() will cause its "socket" into TIME_WAIT. 
> It's like a quarantine to avoid late arriving packets of the old 
> connection from being confused with a new connection using the same 
> port. A major flaw of TCP if you ask me.

Yes. The first side to do a close will end up in TIME_WAIT. The other 
side will never. You're right.

>> But yes, that could be it. I wonder if eaddrinuse really is returned 
>> in that case. [...]
> I experienced this some time ago writing a benchmark on Linux. I'm quite 
> sure it was eaddrinuse that I got when the port numbers where exhausted.

Hmm. Not a good error code in that case (in my opinion). I should 
probably check if other systems apart from Linux do that... Anyone know?

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email:              ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol



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