Re: [Boost-users] Boost::asio - how to detect if a remote socketsclient has disconnected

Subject: Re: [Boost-users] Boost::asio - how to detect if a remote socketsclient has disconnected
From: Etienne Philip Pretorius (icewolfhunter_at_[hidden])
Date: 2009-07-27 12:17:32

Alex Black wrote:
>> On Sat, Jul 25, 2009 at 1:42 PM, Scott 
>> Gifford<sgifford_at_[hidden]> wrote:
>>     
>>> If the client just disappears, you won't get any notification until 
>>> you try to send data (including the OS sending TCP 
>>>       
>> Keepalives, if they 
>>     
>>> are enabled); then when that data send times out, you will get an 
>>> error, probably on your read or the next time you try to write.
>>>       
>> If the client silently drops off, I wouldn't count on getting 
>> an error from send until your TCP send buffer fills up.  
>> Depending on how large the request file/resource is, you may 
>> never know that the client dropped off.  Writes basically 
>> always succeed if there is space in the buffer.  If the 
>> response fits in the buffer, you'll write, close the socket, 
>> and never get an error.  If the response is larger than the 
>> buffer, you'll fill up the buffer, block (assuming blocking 
>> io) until the send times out, and then possibly get an error 
>> (dependent on your TCP stack impl).
>>     
>
> Thanks for the info. It sounds like there isn't any way to detect this
> then.  
>
> Would doing synchronous writes (instead of asycnchronous writes) make
> any difference?
>   
SO_KEEPALIVE?

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