You would certainly want to employ select() and read() instead of your usual filehandle methods (i.e. '<F>') which block until a linefeed, or the value in $/ if it is set to something else, is received.

The select() function lets you know when there's something to read, which means you can do something else while you're waiting, such as time-out if nothing happens.

This program should give you the data as it comes in from a socket: 
#!/usr/bin/perl -w

use strict;
use IO::Socket;

my ($host) = "www.perlmonks.org";
my ($port) = "http(80)";

my ($socket) = new IO::Socket::INET (PeerAddr => $host,
                                     PeerPort => $port,
                                     Proto    => 'tcp');

die "Can't connect to $host:$port\n" unless $socket;

my ($rfd)        = '';          # Must be initialized by string,
                                # not numeric
my ($timeout)    = 5.0;         # 5s timeout
my ($block_size) = 10_000_000;  # Buffer "size" at ~10MB

$|++;   # Unbuffer STDOUT

# Send a sample transaction via HTTP
$socket->write ("GET / HTTP/1.0\r\nHost: $host\r\n\r\n");
$socket->flush();

# Wait loop to receive content
while (1)
{
        # Set the bit-flag for the socket you are waiting on = 1
        vec ($rfd, $socket->fileno(), 1) = 1;

        # Wait for something to happen
        if (select ($rfd, undef, undef, $timeout) >= 0
         && vec($rfd, $socket->fileno(), 1))
        {
                # Something came in!
                my ($buffer);

                # Check what it is by calling read() on the socket
                my ($result) = $socket->read ($buffer, $block_size);

                # Print out what came in
                print $buffer;

                # Drop out of the loop if read() returns a zero
                # value, indicating EOF.
                last unless $result;
        }
        else
        {
                # Timed out on the select(), so bail out.
                last;
        }
}

[download]
I haven't used IO::Socket much, so this was interesting practice. Normally, I just use Socket, which is a far sight better than the Perl4 method using pack(). Hash-style named parameters are all the rage these days, and I'm not complaining. I really should port all my stuff over as soon as I can.

Additionally, you can set the timeout parameter of the select() call to be 0 which means that select() will return immediately, without waiting. This is useful if you need to check if some new data has arrived, but have better things to do than wait around for it.

In reply to Re: Re: Re: how do I read from a socket one byte at a time? by tadman
in thread how do I read from a socket one byte at a time? by reyjrar

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