[erlang-questions] Noob Question ...

Bernard Duggan <>
Fri Mar 6 23:32:34 CET 2009


Valentin Micic wrote:
>> The immediate thing that strikes me is that "127.0.0.1" should be
> {127,0,0,1}. In gen_tcp (erlang in general) the address is a tuple not a
> string.
> 
> This is not correct -- gen_tcp supports string as well as tuple for dotted
> ip address specification

That's true, and for most cases it will work fine, however if you pass
gen_udp a string address it will always call (from memory) gethostbyname
- I presume the same probably applies to gen_tcp.  This turns out to be
a relatively slow operation - if you're only doing one (or even a
hundred) lookups, it's not an issue - we started to strike performance
problems, however, doing large amounts of gen_udp:send operations with
an IP passed as a string.  These went away when we changed it to a tuple.

It's not going to be a problem here, but using the tuple form is
probably a good habit to get into so that it doesn't bite you in the future.

Cheers,

B



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