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From: Robert Watson <rwatson@FreeBSD.org>
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To: Yoshihiro Ota <ota@j.email.ne.jp>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: 2 uni-directional TCP connection good?
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On Fri, 20 Mar 2009, Yoshihiro Ota wrote:

> 1. With TCP connections, only sender side can detect some communication 
> issues passively if happened.  By using two connections, you lost that 
> ability by your self.  I agree on this one.

Could you expand a bit on this point?  While the connection creation process 
(usualy) asymetric, once the connection is built it's essentially the same 
state machine on both sides of the connection, and socket semantics with 
respect to the state machine are effectively identical.  Application on both 
sides should be able to detect disconnect, monitor connection state using 
TCP_INFO, etc.

Robert N M Watson
Computer Laboratory
University of Cambridge