Behavior with/without KEEPALIVE (was Problem with binding of socket addresses)

[Peter Whittaker]

In article <1990Dec10.194130.20414 at athena.mit.edu> jik at athena.mit.edu (Jonathan I. Kamens) writes:
>In article <epeterso.660257641 at houligan>, epeterso at houligan.encore.com (Eric Peterson) writes:
>|> However, the server occasionally hits a bug and core dumps or dies off
>|> in some other way.  But it dies off and closes its end of the

 ... and the rest is deleted....

Related question:

I've already discovered the whims and wonders of SO_REUSEADDR:  my problem
is an application that uses SO_KEEPALIVE, as well.  I won't go into the 
particulars, but could someone outline the differences in behavior between
a client (as described below) using SO_KEEPALIVE, and one not using 
SO_KEEPALIVE?

The client/server relationship:  server binds, listens, accepts, then 
dies (either host goes down or server crashes/is killed).  Kernel then
attempts to close socket.  (Obv.  it's a TCP socket).

The client connects, then does some other stuff 
(i.e. sleep(until_server_is_dead);).
As I understand it, this is what happens when various functions are used
against the socket (NOTE:  no data transfer is pending:  either all data
has been transferred, or none was transferred, before the server died.).

		without  SO_KEEPALIVE		with SO_KEEPALIVE

read()		retcode==-1, errno==?		retcode==-1, errno==?
		(or maybe retcode 0, EOF read in?)
write()		retcode==-1, errno==?		SIGPIPE raised

select()	?? (readfds set true?,		?? (readfds and excepfds
		    EOF pending?)		    set true, EOF pending?)
close()		socket is closed.		socket is closed (*).

(*)-if implementation is correct:  HP-UX 6.5 clients using SO_KEEPALIVE
    never let the socket be closed.  They ACK the server-side FIN_ACK,
    but keep sending keepalives:  they never send their own FIN_ACK, so 
    server never sends RST (server-side kernel ACKs the keepalives).
    Socket is never closed.

advThanksance (<- isn't tm'ed, I hope?)

--
Peter Whittaker      [~~~~~~~~~~~~~~~~~~~~~~~~~~]   Open Systems Integration
pww at bnr.ca           [                          ]   Bell Northern Research 
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