Re: socket in use

["Patrick Townsend" <patownsend@xxxxxxxxxxxxxx>]

Steve,

If you are using setsockopt() to set the socket as re-usable you should be
fine. The socket will show up in NetStat for a period of time with a "fin"
status until the system clears it. But this should not cause a problem.

Patrick
---
IBM AS/400 communications, FTP automation, EDI translation, PGP encryption,
and eCommerce software and consulting services.

http://www.patownsend.com

----- Original Message -----
From: "Steve Richter" <srichter@AutoCoder.com>
To: <MIDRANGE-L@midrange.com>
Sent: Wednesday, July 25, 2001 11:18 AM
Subject: socket in use


> Socket people,
>
> I am getting an intermitent "socket in use" error in my as400 socket
server
> pgm as I test my win95 to as400 socket code.
>
> Even though the shutdown( ) and close( ) functions run without error, the
> next time I run my pgm, a "socket in use" error occurs on the Bind( )
stmt.
> And NetStat shows my prev use of the socket still in a listen state on the
> socket.
>
> By using SetSockOpt( ), I think I have solved the problem. But varying the
> use of shutdown( ) and close( ) also reduced the frequency of the in use
> condition.
>
> My question: Why does the correct use of shutdown( ) and close( ) not
always
> free the socket?
>
> Is there some timeout value that can be set?
>
> Also, is there an api equivalent of NetStat?  When my pgm gets an "in use"
> return code, can it find out what job is using the socket?
>
> And,  Can my pgm forcefully free up a socket that it knows is not really
in
> use?
>
>
> Thanks,
>
> Steve Richter
>
>
> Here are the variations of the code of the server pgm:
>
>
> This code gets the most "in use" errors. ( more than half the time )
>  C                   Eval      SD = Socket (AF_INET: SOCK_STREAM: 0 )
>
>  C                   Eval      SocketAddr = *ALLX'00'
>  C                   Eval      SinFamily  = AF_INET
>  C                   Eval      SinPort    = 3005
>  C                   Eval      SinAddr    = INADDR_ANY
>  C                   Eval      rc = Bind (SD: %ADDR(SocketAddr) :
> %SIZE(SocketAddr))
>
>  C                   Eval      rc = Listen (SD: 1)
>
>  c                   Eval      SD2 = Accept( SD: %Addr(AccpAddr):
> %Addr(AccpAddrLgth) )
>
>  C                   Eval      Lx = Recv( SD2: %Addr(SocketData) :
> %Size(SocketData) : 0 )
>
>  c                   Eval      Rc = SysShutdown( SD: 2 )
>
> c                   Eval      Rc = SysShutdown( SD2: 2 )
>
>  c                   Eval      Rc = Close( SD )
>
> c                   Eval      Rc = Close( SD2 )
>
>
> By shutting down the Listen socket (SD) immed after the Accept( ), the
inuse
> error occurs maybe 20 pct of the time.  ( also by running shutdown(sd),
> close(sd), shutdown(sd2), close(sd2) )
>  C                   Eval      SD = Socket (AF_INET: SOCK_STREAM: 0 )
>
>  C                   Eval      rc = Bind (SD: %ADDR(SocketAddr) :
> %SIZE(SocketAddr))
>
>  C                   Eval      rc = Listen (SD: 1)
>
>  c                   Eval      SD2 = Accept( SD: %Addr(AccpAddr):
> %Addr(AccpAddrLgth) )
>
>
>  c                   Eval      Rc = SysShutdown( SD: 2 )
>
>  c                   Eval      Rc = Close( SD )
>
>  C                   Eval      Lx = Recv( SD2: %Addr(SocketData) :
> %Size(SocketData) : 0 )
>
> c                   Eval      Rc = SysShutdown( SD2: 2 )
>
> c                   Eval      Rc = Close( SD2 )
>
>
>
> Best results are had by running SetSockOpt( ) to make the socket reusable.
>  C                   Eval      SD = Socket (AF_INET: SOCK_STREAM: 0 )
>
>  c                   Eval      rc = SetSockOpt( SD : SOL_SOCKET :
> SO_REUSEADDR :
>  c                                              %Addr(OptVal) :
> %Size(OptVal) )
>
>  C                   Eval      rc = Bind (SD: %ADDR(SocketAddr) :
> %SIZE(SocketAddr))
>
>  C                   Eval      rc = Listen (SD: 1)
>
>  c                   Eval      SD2 = Accept( SD: %Addr(AccpAddr):
> %Addr(AccpAddrLgth) )
>
>
>  c                   Eval      Rc = SysShutdown( SD: 2 )
>
>  c                   Eval      Rc = Close( SD )
>
>  C                   Eval      Lx = Recv( SD2: %Addr(SocketData) :
> %Size(SocketData) : 0 )
>
> c                   Eval      Rc = SysShutdown( SD2: 2 )
>
> c                   Eval      Rc = Close( SD2 )
>
>
>
>
>
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