On Thu, Sep 26, 2013 at 11:40:56AM +1200, Gavin Lambert wrote:
On 9/26/2013 9:36 AM, Quoth Chris Verges:
However, if I physically remove the network interface -- such as yanking the USB adapter out of its socket -- the TCP session stills reports as ESTABLISHED via netstat and the application receives no read error.
I'm at a bit of a loss how this is possible when the underlying OS shows that the interface no longer exists yet the socket is blocking away happily. Has anyone else experienced similar symptoms? Any advice?
This is normal for TCP connections. If you only have outstanding read operations you cannot detect non-graceful shutdowns.
Thanks for the quick reply and insight. I'm floored that the physical interface and/or IP address being removed from the system doesn't cause a related-socket closing. I now understand that this type of functionality is more of a kernel mod than a Boost one.
However the next time you attempt to write to the socket you will get a disconnection error.
Having a "null message" (nop, heartbeat, whatever) should do what is desired, agreed. However, the link is a pay-per-byte thing. I'd prefer to not pay for null. :-) Do you happen to know if writing a zero-length message would be enough to trigger the socket layers to reset without forcing data across the physical layer? (I'm in the middle of coding it up as a test, but figured I'd ask just in case you happened to know.) Much appreciation for your reply, Chris