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(gawkinet.info)Troubleshooting

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Troubleshooting Connection Problems
===================================

   It may well be that for some reason the above program does not run
on your machine. When looking at possible reasons for this, you will
learn much about typical problems that arise in network programming.
First of all, your implementation of `gawk' may not support network
access because it is a pre-3.1 version or you do not have a network
interface in your machine.  Perhaps your machine uses some other
protocol like DECnet or Novell's IPX. For the rest of this major node,
we will assume you work on a Unix machine that supports TCP/IP. If the
above program does not run on such a machine, it may help to replace
the name `localhost' with the name of your machine or its IP address.
If it does, you could replace `localhost' with the name of another
machine in your vicinity. This way, the program connects to another
machine.  Now you should see the date and time being printed by the
program.  Otherwise your machine may not support the `daytime' service.
Try changing the service to `chargen' or `ftp'. This way, the program
connects to other services that should give you some response. If you
are curious, you should have a look at your file `/etc/services'. It
could look like this:

     # /etc/services:
     #
     # Network services, Internet style
     #
     # Name     Number/Protcol  Alternate name # Comments
     
     echo        7/tcp
     echo        7/udp
     discard     9/tcp         sink null
     discard     9/udp         sink null
     daytime     13/tcp
     daytime     13/udp
     chargen     19/tcp        ttytst source
     chargen     19/udp        ttytst source
     ftp         21/tcp
     telnet      23/tcp
     smtp        25/tcp        mail
     finger      79/tcp
     www         80/tcp        http      # WorldWideWeb HTTP
     www         80/udp        # HyperText Transfer Protocol
     pop-2       109/tcp       postoffice    # POP version 2
     pop-2       109/udp
     pop-3       110/tcp       # POP version 3
     pop-3       110/udp
     nntp        119/tcp       readnews untp  # USENET News
     irc         194/tcp       # Internet Relay Chat
     irc         194/udp
     ...

   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
running some flavor of Microsoft Windows usually do _not_ support such
services.  Nevertheless, it _is_ possible to do networking with `gawk'
on Microsoft Windows.(1) The first column of the file gives the name of
the service, the second a unique number, and the protocol that one can
use to connect to this service.  The rest of the line is treated as a
comment.  You see that some services (`echo') support TCP as well as
UDP.

   ---------- Footnotes ----------

   (1) Microsoft prefered to ignore the TCP/IP family of protocols
until 1995. Then came the rise of the Netscape browser as a landmark
"killer application." Microsoft added TCP/IP support and their own
browser to Microsoft Windows 95 at the last minute. They even
back-ported their TCP/IP implementation to Microsoft Windows for
Workgroups 3.11, but it was a rather rudimentary and half-hearted
implementation. Nevertheless, the equivalent of `/etc/services' resides
under `c:\windows\services' on Microsoft Windows.