UNIX domain socket problem

UNIX domain socket problem

[Bin Chen]

Sorry for cross post, it has been posted on
comp.os.linux.development.apps.

I wrote a domain socket sever, which is a STREAM type, let it listen a
sun_path, and in a while loop it accept new connections. I analyze it
using netstat.

Abstractly, the communication need two end. Even the listen socket is
only one, each time the accept returns, there should be two end
produced: one by connect() issued by client, one by accept() issued by
server. These two should have different inode number.

What is strange is that I sometimes find the RefCnt of some unix domain
socket have values 2,3,4,5,6,7 or even 258, if each connection in
stream should be in pair, why this problem occurs?

Thanks.
Binary

Re: UNIX domain socket problem

[Bernd Petrovitsch]

On Tue, 2006-11-07 at 09:47 +0800, Bin Chen wrote:
> Sorry for cross post, it has been posted on
> comp.os.linux.development.apps.
> 
> I wrote a domain socket sever, which is a STREAM type, let it listen a
> sun_path, and in a while loop it accept new connections. I analyze it
> using netstat.
> 
> Abstractly, the communication need two end. Even the listen socket is
> only one, each time the accept returns, there should be two end
> produced: one by connect() issued by client, one by accept() issued by
> server. These two should have different inode number.

Why should they?
The filename (actually and more to the point: the i-node) in the
filesystem is just an "anchor" so that the clients can find the server
(if you have several servers on your system, they *must* have different
filenames to bind(2) to).

> What is strange is that I sometimes find the RefCnt of some unix domain
> socket have values 2,3,4,5,6,7 or even 258, if each connection in
> stream should be in pair, why this problem occurs?

Probably (because I didn't look at source code) because every connect(2)
and/or accept(2) sys-call increments it.
And BTW I assume that you meand the in memory ref count, not the one in
the inode on the disk (which is incremented with hardlinks).

	Bernd
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