Re: Sockets, signal and HTTP server

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Yes, the HTTP server also uses signals, so your program is conflicting 
with the way signals are handled in the HTTP server.

Consider using non-blocking sockets for timeouts rather than signals.


On 10/16/2014 9:16 AM, j.beckeringh@xxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
> Based on the highly recommended examples from Scott Klement I created
> programs (yes David, RPGLE programs :-) that communicate with scales
> through sockets. I use sigaction and alarm to handle timeouts. Basic flow
> of events:
>
> - Register signal handler; save original signal handler (sigaction)
> - Create socket
> - Set alarm to 10 seconds
> - Connect to socket
> - If connected reset alarm, send command, receive data
> - Close socket
> - Restore original signal handler
>
> This works great from a 5250 program. By defining the alarm time as an
> entry field I can vary the time to timeout (very useful when debugging);
> if I try connect to a non-existing IP address I get a timeout in the
> specified time.
>
> But if I try the same from a program that runs in the HTTP server (with a
> call stack that includes Net.Data - DB2WWW) the signal handler never gets
> called.
>
> In debug I can see (trying to connect to a non-existing IP-address):
> - sigaction returns 0, indicating that registering the signal handler was
> successful; the data structure for the original signal handler contains
> data
> - alarm(10) return 0, indicating that no alarm was active; if I call alarm
> twice, the second call returns something between 0 and 10, indicating that
> the previous call was succcesful
> - connect waits for 3 minutes and 6 seconds before returning 3447 - A
> remote host did not respond within the timeout
> - the signal handler never gets called
>
> Anybody any idea what might be the problem? Could it be a conflict with
> the HTTP server?
>
> Release 7.1, TR7.
>
> Joep Beckeringh