Re: [gawk] problem with TCP/IP internetworking feature

[Stepan Kasal]

On Wed, Aug 20, 2003 at 12:43:47PM +0100, Samson Abramsky wrote:
> running gawk version 3.1.3

> "/inet/tcp/0/localhost/daytime" |& getline
> print $0
> close("/inet/tcp/0/localhost/daytime")

> gawk; foo:2 fatal: can't open two way socket
> '/inet/tcp/0/localhost/daytime' for input/output (No such file or
> directory).

> I have verified that `localhost' is present in /etc/hosts, and that
> `daytime' is present in /etc/services.

Your host doesn't support the daytime service.  You have to try another
service instead of "daytime".  If there is sendmail or another SMTP
daemon running on your computer, "smtp" should work.  If you run an
ftp daemon, try service "ftp".

Or, supposing the computer is connected to the Internet, you can try
the following:

BEGIN {
service = "/inet/tcp/0/atrey.karlin.mff.cuni.cz/daytime"
# service = "/inet/tcp/0/matsrv.math.cas.cz/smtp"
service |& getline
print $0
close(service)
}

I hope you find at least one working combination.

Back to the original question: in order to be able to contact a TCP port
("a service"), the computer has to "listen" on the port.  On Linux and
other Unix style systems, this usually means that a daemon is running and
listening on that port.  Your computer doesn't run any daemon listening
on the "daytime" port.

The gawkinet manual says (about /etc/sevices):
|    Here, you find a list of services that traditional Unix machines
| usually support. If your GNU/Linux machine does not do so, it may be
| that these services are switched off in some startup script. Systems

So, /etc/services is a list of services "Unix machines usually support".
It's not the list of services the actual machine supports.

Perhaps the wording should be changed to:
  Here, you find a list of services that Unix machines often support.
  It depends on the configuration of your GNU/Linux or Unix system,
  which of them are actually running.

Hope this explains it,
        Stepan Kasal