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#!/usr/bin/env perl
# A simple TCP client that sends some data and expects a response.
# Usage: tcp_client.pl HOSTNAME PORT DATA1 RESPONSE1
# DATA: hex-encoded data to send to the server
# RESPONSE: regexp that must match the server's response
use warnings;
use strict;
use IO::Socket::INET;
# Pack hex digits into a binary string, ignoring whitespace.
sub parse_hex {
my ($hex) = @_;
$hex =~ s/\s+//g;
return pack('H*', $hex);
}
## Open a TCP connection to the specified host and port.
sub open_connection {
my ($host, $port) = @_;
my $socket = IO::Socket::INET->new(PeerAddr => $host,
PeerPort => $port,
Proto => 'tcp',
Timeout => 1);
die "Cannot connect to $host:$port: $!" unless $socket;
return $socket;
}
## Close the TCP connection.
sub close_connection {
my ($connection) = @_;
$connection->shutdown(2);
# Ignore shutdown failures (at least for now)
return 1;
}
## Write the given data, expressed as hexadecimal
sub write_data {
my ($connection, $hexdata) = @_;
my $data = parse_hex($hexdata);
my $total_sent = 0;
while ($total_sent < length($data)) {
my $sent = $connection->send($data, 0);
if (!defined $sent) {
die "Unable to send data: $!";
}
$total_sent += $sent;
}
return 1;
}
## Read a response and check it against an expected prefix
sub read_response {
my ($connection, $expected_hex) = @_;
my $expected_data = parse_hex($expected_hex);
my $start_offset = 0;
while ($start_offset < length($expected_data)) {
my $actual_data;
my $ok = $connection->recv($actual_data, length($expected_data));
if (!defined $ok) {
die "Unable to receive data: $!";
}
if (($actual_data ^ substr($expected_data, $start_offset)) =~ /[^\000]/) {
printf STDERR ("Received \\x%02x instead of \\x%02x at offset %d\n",
ord(substr($actual_data, $-[0], 1)),
ord(substr($expected_data, $start_offset + $-[0], 1)),
$start_offset + $-[0]);
return 0;
}
$start_offset += length($actual_data);
}
return 1;
}
if (@ARGV != 4) {
print STDERR "Usage: $0 HOSTNAME PORT DATA1 RESPONSE1\n";
exit(3);
}
my ($host, $port, $data1, $response1) = @ARGV;
my $connection = open_connection($host, $port);
write_data($connection, $data1);
if (!read_response($connection, $response1)) {
exit(1);
}
close_connection($connection);
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