[olug] questions about socket programming

Jeff Hinrichs - DM&T jeffh at dundeemt.com
Sat Aug 1 22:35:22 CDT 2020

My understanding is that the loop doesn't execute and waits at the
socket_accept statement
which has a comment that is is a blocking call.  Which would mean that no
code beyond that point
is executed unless there is an incoming socket request.

If you put an echo immediately after that statement, nothing should print
until an incoming socket occurs.
You can prove that the PHP loop is not busy by doing so.


On Sat, Aug 1, 2020 at 10:07 PM Lou Duchez <lou at paprikash.com> wrote:

> Thanks! One thing the tutorial clued me into is that it's possible to
> set a backlog on "socket_listen", so I can set a buffer on pending
> connections.  That doesn't change how one codes the socket connection,
> but it seems like it will keep from sending a "busy" signal to every
> connection past the first.
> That tutorial doesn't have any examples of putting a "sleep" in the
> grand loop, though.  I am caught between believing they know what
> they're doing, but also seeing with my own eyes that a lack of a "sleep"
> means eating up a ton of CPU cycles.  I am not so prideful that I assume
> I know better than the tutorial writers, on the other hand the evidence
> of my senses tells me that they left something out.
> On 8/1/2020 10:28 PM, Jeff Hinrichs - DM&T wrote:
> > Not sure what you are trying to accomplish,  but this is a decent
> tutorial
> >
> https://webmobtuts.com/backend-development/introduction-to-php-sockets-programming/
> > what happens depends on if you socket code is async or not and how you
> > write it will determine
> > if that is possible.  The link above shows how to accomplish it in PHP
> (or
> > at least says it does.)
> > I have not tested the code or used PHP in quite some time.  So you milage
> > may vary or someone with more recent PHP fu
> > will pipe up.
> >
> > Good luck with your endeavors
> > -Jeff
> > The other thing I was alluding to is web sockets.
> >
> > On Sat, Aug 1, 2020 at 8:26 PM Lou Duchez <lou at paprikash.com> wrote:
> >
> >> You folks know your socket programming inside out (I bet), so a couple
> >> questions about a PHP socket server I've written.
> >>
> >> First thing the code does is create a socket (let's call it
> >> "$greeter_socket") for fielding incoming connections.  Then a grand loop
> >> happens where I iteratively check for incoming connections on
> >> $greeter_socket, create sockets for bidirectional communications for
> >> each incoming connection, and also do all the reads / writes to all the
> >> bidirectional sockets as needed.  Here are my questions:
> >>
> >> 1) What happens if two people are trying to connect at the same time?  I
> >> imagine that the socket can handle only one connection at a time, so
> >> $greeter_socket will handle whoever got there first, and the other
> >> person will have to try again and again until they get through or their
> >> retry period expires.
> >>
> >> 2) The code examples I've seen do not put any sort of sleep(), usleep(),
> >> or time_nanosleep() in the grand loop. That seems ill-advised to me;
> >> based on my testing, the grand loop consumes a ton of CPU unless I put a
> >> brief sleep (maybe one-tenth second) in each iteration.  Am I wrong to
> >> put the sleep in there?  Am I handling it wrong?
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Jeff Hinrichs

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