Srikanth,

I cant really help you much with the mechanics of threads on the
AS/400.  I've done a LOT of multi-threaded programming, but it has all
been Win32 based.

But I can tell you there is no real difference between a "thread" and a
"worker thread".  It is just how you use them.

You can create a thread for each client connecting to your server.
That thread would then handle everything associated with that client
and basically act like none of the other threads/clients exist.  This
is by far the easiest model.

With "worker threads" or also known as a "thread pool", your server
starts a fixed number of threads.  Then when there is work to be done,
the main thread allocates that work to one of these worker threads.
That thread then handles a unit of work (typically a transaction) for
the client and then passes the socket back to the main thread.  The
worker thread then back into the "available thread pool".

Sort of like the line for tellers at the bank.  There are 5 tellers and
only one door into the lobby.  When you enter the lobby, you get into
line until one of the tellers (worker threads) is available.  The
teller then handles your transaction and you leave and the teller then
goes to the next person in line.  If nobody is in line, they just stand
there waiting.

Bob

-----Original Message-----
From: c400-l-admin@midrange.com [mailto:c400-l-admin@midrange.com]On
Behalf Of Srikanth_D
Sent: Sunday, June 02, 2002 11:09 PM
To: c400-l@midrange.com
Subject: RE: [C400-L] select()

thanks a lot bob, i was out on weekend so this delay in response.
i got your point.

i am still in dark regarding allocating a thread/worker thread, i am
using
pthread_create() . what exactly is pthread_create(), a worker thread or
am i
allocating a thread. to be honest i am a beginner in multithreaded
programming, if you can pass on URLs/any documents on multithreading on
AS/400 it will be of great help.

best rgds.,
srikanth d


> ----------
> From:         Bob Crothers[SMTP:bob@cstoneindy.com]
> Reply To:     c400-l@midrange.com
> Sent:         Friday, May 31, 2002 8:02 PM
> To:   c400-l@midrange.com
> Subject:      RE: [C400-L] select()
>
> Srikanth,
>
> If you make your server app multi-threaded, you wont have to mess
with
> select() at all.
>
> Exactly how you structure your app will depend on many things like
are
> the connections persistent or "connect, do a single transaction,
> disconnect"?
>
> If they are persistent, what kind of volume?
>
> Answers to these questions will help you determine your threading
> model.  Eg: Simply allocate a thread to service each client or use
> "worker" threads.  Allocating a thread per client works well when a)
> number of concurrent clients is small -or-b) volume from each client
is
> high -or- c) you want to keep things simple and performance isn't an
> issue.
>
> Regardless of the thread model you use, the socket logic is fairly
> simple:
>
> In the main listener thread:
>
> 1) bind()
> 2) listen()           // wait for a new connection request
> 3) accept()   // get the new connect request
> 4) givedescriptor()   //set up to pass the socket to a thread
> 5)                    // depending on thread model, figure out what
thread
> to send the
> socket over to
> 6) Go back up and do your listen() again and wait for next connect
> request.
>
> Then in the processing threads:
>
> 1) takedescriptor()
> 2) now act like the rest of the world doesn't exist.  Use blocking
> send/receives etc.
>
> If you are dealing with a lot of clients, the above logic will have
to
> be modified somewhat, but the concept is similar.
>
> I use give/takedescriptor because when I wrote the socket my server
> that runs on the as/400, "threads" didn't exist in os/400.  So I had
to
> use jobs instead of threads and the give/takedescriptor was the only
> way to pass the sockets between jobs.
>
> In the PC world, there are much easier ways to pass a socket between
> threads and if they are available for you to use on the AS/400, you
> should probably use them.
>
> Regards,
> Bob Crothers
> Cornerstone Communications
> http://www.cstoneindy.com
>
>
>
>
> -----Original Message-----
> From: c400-l-admin@midrange.com [mailto:c400-l-admin@midrange.com]On
> Behalf Of Srikanth_D
> Sent: Friday, May 31, 2002 4:34 AM
> To: c400-l@midrange.com
> Subject: [C400-L] select()
>
> hi all,
>
> i am a little confused on how to use select() in a socket program.
here
> is
> the deal.
>
> client connects to a server to accomplish a transaction, let us say
> account
> balance enquiry. right now my code blocks on a send() and recv(), for
> e.g.
> client send()s the account number and blocks on a recv() to get the
> balance
> of the account. i would like to eliminate these blocking. i think
using
> select() would be the choice for that, but what would be the basis to
> set
> values to the struct timeval which is the fifth parameter in
select().
> can i
> use select() in a multithreaded environment. for complex transactions
> (like
> fund transfer between two accounts) i have various send() and recv(),
> do i
> need to code select() before each send() and recv().
>
> please help me on this.
>
> thanks in advance.
> -srikanth d
>
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