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

On Sat, Jul 25, 2009 at 1:42 PM, Scott Gifford wrote:

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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?