#!/bin/perl
# Perl server-socket example

# this version does not use the IO::Socket library, so it's more like C than Java

use Socket;
require "byteordering.pl";  # you'll need to download this too.

my $PORT = $ARGV[0]; # port determined by command-line arg
my ($saddr, $caddr);
my $buffer = "abcdefghijklmnopqrstuvwxyz";   # binary (string) data buffer;
my $d = 3.14;      # double value
my ($x, $y, $i, $j); # utility
$byteorder = endiancheck();
# note: the data buffer cannot be empty!

socket(sfd,AF_INET,SOCK_STREAM,getprotobyname('tcp')) || die "error";

$saddr = sockaddr_in($PORT,INADDR_ANY);
bind(sfd,$saddr) || die "failed to bind";
listen(sfd,32);

while (1)  # server loop
  {
     accept (cfd,sfd);  # accept connection, create communication socket cfd
     print "connection established\n";
     # write an integer in binary mode
     $x = 10;  # at this point, 10 is actually "10" !!!
     $y = pack("i",$x);  # convert to binary representation (pack into an integer).
     $y = htonl($y);     # host to network byte ordering
     syswrite(cfd,$y,4,0);  # write 4 bytes starting from \$$y + 0
     syswrite(cfd,$buffer,$x,0);  # write $x bytes
     $i = sysread(cfd,$d,8,0);  # read 8 bytes  - treated as a string of 8 chars
     if ($i != 8) {die $!;}
     $d = unpack("d",$d);       # convert to numerical representation;

     # the conversion between data formats is a bit harder than in C/Java because
     # Perl does not use much type information.

     # if we were just communicating strings, or with another perl host, then
     # socket IO would be much simpler: we can use <> to read and print to write.
     # - see the filecopy program and the perl http client for example.  The only
     # slight complication in that case is the need for "autoflush".

     close(cfd);
  }