modprobe will only load the necessary kernel modules to make the chipsets on your serialport card work. To test what port gets assigned to them, maybe check the boot logs, or maybe you could loop thru the possibilities and see what happens? 
#!/usr/bin/perl -w
use Device::Modem;

# fake array :-)  I'm lazy
foreach my $port qw(  /dev/ttyS0  ..  /dev/ttyS24 ){

my $modem = new Device::Modem( log =>'file,modemlog',
      port => $port ) || die "no $port: $!\n";

$modem->reset(); #hangup + attention + restore setting 0 (Z0)
}

[download]
I'm not really a human, but I play one on earth CandyGram for Mongo

In reply to Re: Device::SerialPort and new RS-232 cards by zentara
in thread Device::SerialPort and new RS-232 cards by Bruce32903

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.