Re: Socket Keepalive

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Hmmm...  i don't have an example handy, but...  I would recommend two 
calls to setsockopt().  The one Kevin shows is one of them, but then 
also one to set TCP_KEEPALIVE which lets you set the keepalive interval.

Like I said before, I think relying on the CHGTCPA option is not a good 
idea, some day someone will change that setting for something unrelated 
and screw you up.

The stuff in CHGTCPA should only be used as "defaults".  When an 
application has a speciic need for something (like your need for keep 
alives) it should be coded into that application explicitly.

So, two calls to setsockopt().  One wit SOL_SOCKET and SO_KEEPALIVE and 
one with IPPROTO_TCP and TCP_KEEPALIVE.  This second option should tell 
it how often to send the keepalives.

-SK

On 9/2/2015 1:49 PM, Kevin Bucknum wrote:
>  From an old server program, the only one we ever turned keepalive on
> for.
>
> Eval      Rc = setsockopt(sd: sol_socket
>                              : so_keepal
>                              : %addr(optval)
>                              : %size(optval))
>
> sd is the socket descriptor we got from the call to socket.
> The program I cut the above code from is really old. Here is the current
> definition in my copybook.
> D*                                          keep connections alive
> D SO_KEEPALIVE    C                   25
> D*                                                socket layer
> D SOL_SOCKET      C                   CONST(-1)
>
> d optval          s             10u 0 inz(1)
>
> CHGTCPA has the setting to control the interval.
>                        Change TCP/IP Attributes (CHGTCPA)
>
> Type choices, press Enter.
>
> TCP keep alive . . . . . . . . .   5             1-40320, *SAME, *DFT
>
> The help for that option.
>              TCP keep alive (TCPKEEPALV) - Help
>
> Specifies the amount of time, in minutes, that TCP waits
> before sending out a probe to the other side of a
> connection.  The probe is sent when the connection is
> otherwise idle, even when there is no data to be sent.
>
> The transmission of keep-alive packets is controlled by
> individual sockets applications through use of the
> SO_KEEPALIVE socket option.  For more information see the
> Socket programming topic collection in the IBM i
> Information Center at
> http://www.ibm.com/systems/i/infocenter/.
>
>
>
>
> Kevin Bucknum
> Senior Programmer Analyst
> MEDDATA/MEDTRON
> Tel: 985-893-2550
>
> -----Original Message-----
> From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Jeff
> Young
> Sent: Wednesday, September 02, 2015 1:20 PM
> To: RPG programming on the IBM i (AS/400 and iSeries)
> Subject: Socket Keepalive
>
> In a previous post, it was recommended that I use the SO_KEEPALIVE in
> the setsockopt to enable my program to use this.
> I have not been able to find any good example on how to set this and how
> to configure the keepalive interval.
> Does anyone have an example of this that I can refer to?
>
>
> Jeff Young
> Sr. Programmer Analyst
> --
> This is the RPG programming on the IBM i (AS/400 and iSeries) (RPG400-L)
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