[erlang-questions] Long polling

Kaiduan Xie <>
Tue Jul 17 17:34:46 CEST 2012

I assume that you are talking about the TCP NAT keep-alive time.
Please check the following paper,


Please look at the Timer section in the survey.

Why you need to use HTTP long poll? You can just use a persistent
TCP/TLS connection and periodically send keep-alive message to keep
the TCP/TLS connection alive.

Or you can use Websocket, it is designed to replace long poll.


On Tue, Jul 17, 2012 at 11:01 AM, Gleb Peregud <> wrote:
> On Tue, Jul 17, 2012 at 4:57 PM, Gordon Guthrie <> wrote:
>> Folks
>> I am building a softphone which needs to register with the server to say "I
>> am available" for incoming calls.
>> So it makes an HTTP POST request to the server and that notifies the
>> softphone gen_srv that is is available.
>> At that point I leave the TCP request hanging on a receive waiting for a
>> notification that the socket has been torn down (and which point it
>> unregisters the phone).
>> My question is: how long can I leave the request up? Infinity? or do I need
>> to have a timeout/reregister cycle setup?
> You have to cycle it. Some proxies timeout connections after 30
> seconds, some after 45 some after 60. It is very tricky to get it
> right for all browsers and all platforms. Generally if you want a
> robust solution use something like SockJS or Socket.IO or Bullet.
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