Socket shutdown: difference between Windows and Linux

The behaviour of close() and closesocket() cobmined with SO_LINGER is quite clear for me. I'm still confused about shutdown(): does SO_LINGER apply to shutdown in the same way?
 
MSDN "The shutdown function does not block regardless of the SO_LINGER setting on the socket".

GNU documentation says: "Stop trying to transmit data from this socket. Discard any data waiting to be sent. Stop looking for acknowledgement of data already sent; don't retransmit it if it is lost."

It seems to me, that calling shutdown() just discards any data to be sent through the socket -- I just want to be sure. If I'm right I can call shutdown() followed by close[socket](), to break connection without blocking -- is it true?

>>If I'm right I can call shutdown() followed by close
>>[socket](), to break connection without blocking -- is
>>it true?

That depends - 'shutdown()' itself won't block. If you want to totally get rid of the socket, calling 'shutdown ( s, SD_BOTH);' should be fine. There are however other possibilities, like e.g. the following:

"2.6 When should I use shutdown()?
From Michael Hunter ( mphunter@qnx.com):

shutdown() is useful for deliniating when you are done providing a request to a server using TCP. A typical use is to send a request to a server followed by a shutdown(). The server will read your request followed by an EOF (read of 0 on most unix implementations). This tells the server that it has your full request. You then go read blocked on the socket. The server will process your request and send the necessary data back to you followed by a close. When you have finished reading all of the response to your request you will read an EOF thus signifying that you have the whole response. It should be noted the TTCP (TCP for Transactions -- see R. Steven's home page) provides for a better method of tcp transaction management"

(from http://www.softlab.ece.ntua.gr/facilities/documentation/unix/unix-socket-faq/unix-socket-faq-2.html#ss2.5)

Thanks for your help. I'll ask Community Support to split points between you in a week. I'm still waiting for any new comments, if someone know something that jkr and bryanh don't.

well, having written a big win32 web server, I've had to deal with shaking off connections that are no longer welcome.

I've given up on shutdown because it was too wimpy.

Under Windows, I do
WSAAsyncSelect(socket, windowhandle, 0, 0) ;
u_long ul = 0 ; ioctlsocket(socket, FIONBIO, &ul) ;
LingerStruct ls = {1, 0} ;
setsockopt(socket, SOL_SOCKET, SO_LINGER, (LPSTR)&ls, sizeof(ls)) ;
if (SOCKET_ERROR == closesocket(socket))
  AddSocketToKillList(socket) ;

the WSAAsyncSelect is needed because I used the async notifications.
The FIONBIO sets the socket as non blocking to avoid surprises.

TIP: also pay attention to the closesocket return value.
If it's not happy, it's not closed.

I keep a list that I torture later at intervals until they finally break off.

The test that they broke off is with a combination of getsockopt, getpeername, getsockname and setsockopt.
If the socket accepts to be manipulated, it's deemed to be alive and I keep trying to kill it.

I didn't do many unix experiments lately so I can't guarantee this will help on that side of the project.

Hello all

Robson has asked to split the points

http://www.experts-exchange.com/Community_Support/Q_20355901.html

i lower the points here to give the user a chance to ask points for questions for the other two experts

JGould-EE Moderator

Thaks for your comments! I'll give points to remster and jkr in separate questions just as CS said. I apologise for keeping you waiting for so long (ether EE was down, or our company network unusable).