On Dec 8, 2007 8:32 AM, Niu Kun <[EMAIL PROTECTED]> wrote:
> Dear all,
> I'm new here.
> I've got a number larger than 128.
> I want to send it by socket.
> I find that if print the number directly, I'll print the number in ascii
> format.
> So I'll have 3 separate numbers transmitted.
> But I only want to transmit one byte.
> How can I do so?
>
> Thanks for any help.
I believe you are looking for the pack* function. It will let you
take a list Perl scalars and convert them into the specified
representation. You might also be looking for the chr** function
which will return the appropriate character; however, since Perl now
uses UTF-8 the chr is no longer guaranteed to produce a value that
takes up only one byte. For instance, chr(0x263a), WHITE SMILING
FACE, returns three bytes (E2, 98, and BA). The opposite functions
are unpack*** and ord****. Also note that the largest value one byte
can hold is 255 (if it is unsigned, 127 if it is signed).
Off hand I would say you want something like
die "can't fit $val in an unsigned byte" if $val < 0 or $val > 255;
print $sock pack "C", $val;
on the sending end and
sysread $sock, $buf, 1;
my $val = unpack "C", $buf;
on the receiving end; however, it a good network protocol will include
a lot more information than this. Perhaps if you explain what you are
trying to accomplish we can point out a higher level interface that
will serve your needs better (handling raw sockets is generally a sign
you are reinventing the wheel).
* see "perldoc -f pack" or http://perldoc.perl.org/functions/pack.html
** see "perldoc -f chr" or http://perldoc.perl.org/functions/chr.html
*** see "perldoc -f unpack" or http://perldoc.perl.org/functions/unpack.html
**** see "perldoc -f ord" or http://perldoc.perl.org/functions/ord.html
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