use IO::Socket::INET;
use IO::Select;
use Errno qw(EAGAIN);

my $timeout = 60;

my $socket = IO::Socket::INET->new(
    PeerAddr => "...",
    PeerPort => "1234",
    Proto => 'tcp',
) or die "Cannot create new socket: $!";;

my $request = "...";

unless ( sock_write($socket, \$request, length($request)) ) {
    die "sock_write: socket write error ($!)";
}

print "wrote $request to the socket\n";

my $len = ...;
my $response = "";

unless ( sock_read($socket, \$response, $len) ) {
    die "sock_read: socket read error ($!)";
}

print "read $response from the socket\n";

exit;

# sock_read(
#  $socket - IO::Socket::INET socket to read from
#  \$msg   - Reference to hold the read data
#  $len    - number of bytes to read from the socket
#)
# returns: original reference to the data, or undef

sub sock_read {
    my $socket = shift;
    my $buf = shift;
    my $len = shift;
    my $offset = 0;
    my $n = 0;

    my $sel = IO::Select->new($socket);

    while ( $offset < $len ) {
        unless ( $socket ) {
            warn "Socket became undef during read!";
            return undef;
        }
        unless ($sel->can_read($timeout)) {
            warn "Socket read timed out";
            return undef;
        }

        $n = $socket->sysread($$buf, $len-$offset, $offset);
        # Check for "Resource temporarily unavailable" error, and clear it.
        # This just means that we can't write to the socket "just now" since it's
        # buffer is full.
        if ($!{EAGAIN}) {
            warn "Socket would read block!";
            $! = 0; # Clear the error
            $n = 0; # "Define" $n
        }
        unless ( defined($n) ) {
            return undef;
        }
        if ((not $!{EAGAIN}) && ($n == 0)) {
            warn "Socket read returned no data: unknown comms error!";
            return undef;
        }
        $offset += $n;
    }

    return $buf;
}

# sock_write(
#  $socket - IO::Socket::INET socket to write to
#  \$msg   - Reference to hold the data to write
#  $len    - number of bytes to write to the socket
#)
# returns: original reference to the data, or undef

sub sock_write {
    my $socket = shift;
    my $buf = shift;
    my $len = shift;
    my $offset = 0;
    my $n = 0;

    my $sel = IO::Select->new($socket);

    while ( $offset < $len ) {
        unless ( $socket ) {
            warn "Socket became undef during write!";
            return undef;
        }
        unless ($sel->can_write($timeout)) {
            warn "Socket write timed out";
            return undef;
        }

        $n = $socket->syswrite($$buf, $len-$offset, $offset);
        # Check for "Resource temporarily unavailable" error, and clear it.
        # This just means that we can't write to the socket "just now" since it's
        # buffer is full.
        if ($!{EAGAIN}) {
            warn "Socket write would block!";
            $! = 0; # Clear the error
            $n = 0; # "Define" $n
        }
        unless ( defined($n) ) {
            return undef;
        }
        if ((not $!{EAGAIN}) && ($n == 0)) {
            warn "socket failed to write any data!";
            return undef;
        }
        $offset += $n;
    }

    return $buf;
}