Re: network time service, non-blocking?

[arnold]

Petr,

Gawk's network support is minimal. In the long run you may
be better off in Python or Go.

Arnold

david kerns <david.t.kerns@gmail.com> wrote:

> On Wed, May 11, 2022 at 1:39 AM Petr Slansky <slansky@gmail.com> wrote:
>
> > Hello Gawk,
> >
> > this is not real bug report, it is something like a feedback. I use gawk
> > 4.1.4.
> >
> > I tried to use gawk for some network service, to report progress of data
> > processed from pipeline to websocket but I think I cannot do that because
> > gawk doesn't support non-blocking sockets. To illustrate that, I use
> > example with simple time service, similar to
> >
> > https://www.gnu.org/software/gawk/manual/gawkinet/html_node/Setting-Up.html#Setting-Up
> >
> > $ cat timesrv.awk
> > # Time server
> > BEGIN {
> >   service = "/inet/tcp/8888/0/0";
> >   while (1) {
> >      time = strftime();
> >      print time;
> >      print time |& service;
> >      close(service);
> >   }
> > }
> >
> > # run it
> > $ gawk -f timeserv.awk
> >
> > # other terminal
> > $ sleep 45; date; curl http://localhost:8888
> >
> > The problem of this server is that it reports "old" time. It samples time
> > to a variable and it waits for an incoming connection from a client, then
> > it reports time and samples new time. When clients don't connect
> > frequently, they get wrong (old) time.
> >
> > Is there a way, to check if client connected to listening socket? Open
> > server socket, do some other tasks and from time to time check if client is
> > connected; when client is connected, serve fresh data otherwise continue to
> > process data. It is possible that I cannot use gawk for my task and I have
> > to use Python, Go or other tool.
> >
> > Petr
> >
>
> you should be using the awk-help mailing list for this question ...
>
> since you are using curl/http to connect (ie have lots of incoming data to
> indicate a new connection)
> just make the blocking read at the top of the loop:
>
> # Time server
> BEGIN {
>   service = "/inet/tcp/8888/0/0";
>   while (1) {
>      service |& getline; # wait for new request
>      time = strftime();
>      print time;
>      print time |& service;
>      close(service);
>   }
> }
>
> this code still only returns the time, (in a non machine friendly format)
> and not a valid http reply, but that's beyond the scope of the OP