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

Sverker Eriksson sverker@REDACTED
Fri Jan 30 16:45:19 CET 2009

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.

> 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.


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