[MacPerl] How to do ICMP Ping from MacPerl

[Mike Wirth]

Title: How to do ICMP Ping from MacPerl

According to the book, "MacPerl - Power and Ease" (Chapter 17, p. 239):

        MacPerl has not implemented the ICMP protocol, used by the Unix
ping program. The Mac interface is incompatible with that of the Unix
   protocol; it would be possible to write an extension for MacPerl to add

        ICMP functionality, but at present none exists.

Too bad, because I really needed ICMP ping to monitor my flakey DSL connection (due to the "well known" sync-no-surf problem with my Alcatel SpeedTouch Home modem -- hangs, probably when the line get noisy, and has to be rebooted or power-cycled.  Let me know if you have any experience with this problem.  Also see the security alert on this modem at http://security.sdsc.edu)

So here's a cheap trick to get this capability from MacPerl.  Sergey Tolkachev in '97-'98 wrote a set of useful HyperCard XCMDs contained in his stack, HyperHTTP.PPC (which you can find on the usual HyperCard archives), and released them as "freeware for non-commercial use".  Since I only needed the ping XCMD, I extracted it with ResEdit to a much smaller separate file, Ping.XCMD, attached here.

Here's a trivial MacPerl script which uses this XCMD to ping my DSL provider's two DNS servers every 5 minutes.  (If I can't get to them, it's certain that my DSL modem is hung.)

========================================

#!perl -w
package Ping;
MacPerl::LoadExternals("Ping.XCMD");

package main;

while (1) {
      print Ping::Ping("206.13.28.12"), " at ", (scalar localtime), "\n";
     print Ping::Ping("206.13.31.12"), " at ", (scalar localtime), "\n";
     sleep 300;
      }

========================================

which produces output like:

206.13.28.12 Alive at Sun May  6 16:00:16 2001
206.13.31.12 Alive at Sun May  6 16:00:16 2001
206.13.28.12 Alive at Sun May  6 16:05:15 2001
206.13.31.12 Alive at Sun May  6 16:05:15 2001
206.13.28.12 Not respond at Sun May  6 16:10:19 2001
206.13.31.12 Not respond at Sun May  6 16:10:24 2001

... sigh, time to reboot the modem...

Note the capitalization of the file and XCMD above.  HyperCard is very casual about capitalization, but MacPerl isn't.

The XCMD is limited; you can't change the ping timeout or the text of the response, but it does what I needed.  If you give it a hostname (e.g., "www.apple.com") rather than a dotted-decimal host address, it'll do a DNS lookup before the ping.  But I wanted to use the test in its most primitive form.

The security alert cited above gives some interesting hints on how to get signal-to-noise (and other operational) data out of the Alcatel modem.  So now that I can "ping" to test if my link is up, I'm getting ready to use Net::Telnet to query the modem on a regular basis to extract S/N data (to see if I can diagnose what's causing the hangs) and to automatically reboot the modem.

Mike Wirth

Palo Alto, CA

PS: Perhaps someone who understands the MacPerl distribution better than I do can put this XCMD and these instructions in an appropriate repository.