php telnet no response from script

Question

I'm running PHP5 on Windows XP Professional. I'm trying to write a telnet php script which simply connects, sends a text string and grabs the response buffer and outputs it. I'm using the telnet class file from here:

http://cvs.adfinis.ch/cvs.php/phpStreamcast/telnet.class.php

which i found in another thread.

<?php 
error_reporting(255);
ini_set('display_errors', true);

echo "1<br>";
require_once("telnet_class.php");

$telnet = new Telnet(); 

$telnet->set_host("10.10.5.7"); 
$telnet->set_port("2002");
$telnet->connect();
//$telnet->wait_prompt();
$telnet->write('SNRD   1%0d');
echo "3<br>";
$result = $telnet->get_buffer();
        echo $result;
        print_r($result);
//        flush_now();
echo "4<br>";

$telnet->disconnect();

?>

I'm not receiving any kind of errors or response. If I send an invalid string, I should get an 'ERR' response in the least however I don't even get that. Any ideas what i could be doing wrong? If I do the same thing from the command prompt, I receive the string output I need. Could this is because the write function is sending

Answer 1

You can't insert hex values like that. The remote process just sees

SRND   1%0d

and now it's waiting for the line to be terminated. Try this

$telnet->write('SNRD   1' . "\r");

or

$telnet->write("SNRD   1\xd");

The double quotes are quite critical, see here

EDIT:

you might try adding some error reporting as right now you don't really check much (error_reporting won't show anything on the errors in the telnet class).... For example:

<?php 
error_reporting(255);
ini_set('display_errors', true);

echo "1<br>";
require_once("telnet_class.php");

$telnet = new Telnet(); 

$telnet->set_host("10.10.5.7"); 
$telnet->set_port("2002");
if ($telnet->connect() != TELNET_OK) {
     printf("Telnet error on connect, %s\n",$telnet->get_last_error());
}
//$telnet->wait_prompt();
if ($telnet->write('SNRD   1' . "\xd") != TELNET_OK) {
     printf("Telnet error on write, %s\n",$telnet->get_last_error());
}

echo "3<br>";
$result = $telnet->get_buffer();
        echo $result;
        print_r($result);
//        flush_now();
echo "4<br>";

$telnet->disconnect();

?>

also, are you sure you need \r\n line termination? write is defined as

function write($buffer, $valeurLoggee = "", $ajouterfinLigne = true){

and does

    if ($ajouterfinLigne){
        $buffer .= "\n";
    }

?

Also, did you test the host and port with the command line telnet client? Like

telnet 10.10.5.7 2002

?

Answer 2

Have you checked how the telnet class works? Maybe it wasn't designed to run under windows. If it's a simple socket that you're speaking to, maybe consider using a regular socket-connection instead.

http://se2.php.net/sockets

If you open up a socket which you don't close, you should se an entry in netstat as long as your script is running.

netstat -na|find ":2002"

Answer 3

After some reading in the source code and on the original (french) site referred to in the header....

<?php 
error_reporting(255);
ini_set('display_errors', true);

echo "1<br>";
require_once("telnet_class.php");

$telnet = new Telnet(); 

$telnet->set_host("10.10.5.7"); 
$telnet->set_port("2002");
if ($telnet->connect() != TELNET_OK) {
     printf("Telnet error on connect, %s\n",$telnet->get_last_error());
}
//$telnet->wait_prompt();
if ($telnet->write('SNRD   1' . "\xd") != TELNET_OK) {
     printf("Telnet error on write, %s\n",$telnet->get_last_error());
}

// read to \n or whatever terminates the string you need to read
if ($telnet->read_to("\n") != TELNET_OK) {  
     printf("Telnet error on read_to, %s\n",$telnet->get_last_error());
}
echo "3<br>";


$result = $telnet->get_buffer();
        echo $result;
        print_r($result);
//        flush_now();
echo "4<br>";

$telnet->disconnect();

?>

Okay, explanation: get_buffer() does just that, read what's in the buffer. To get something in the buffer you have to execute read_to($match) who will read into buffer up to $match. After that, get_buffer should give you the desired string.

EDIT: if you cannot find some string that follows the string you are interested in read_to will end in an error due to this part of the read_to method (translation of original french comment is mine):

    if ($c === false){
     // plus de caracteres a lire sur la socket
     // --> no more characters to read on the socket
        if ($this->contientErreur($buf)){
            return TELNET_ERROR;
        }

        $this->error = " Couldn't find the requested : '" . $chaine . "', it was not in the data returned from server : '" . $buf . "'" ;
        $this->logger($this->error);
        return TELNET_ERROR;
    }

Meaning that when the socket is closed without a match of the requested string, TELNET_ERROR will be returned. However, the string you're looking for should at that point be in the buffer.... What did you put in read_to's argument? "\n" like what I did or just "" ?

EDIT2 : there's also a problem with get_buffer. IMO this class is not really a timesaver ;-)

//------------------------------------------------------------------------
function get_buffer(){
    $buf = $this->buffer;

    // cut last line (is always prompt)
    $buf = explode("\n", $buf);
    unset($buf[count($buf)-1]);
    $buf = join("\n",$buf);
    return trim($buf);
}

It will throw away the last line of the response, in your case the one that contains the answer. I suggest to add a "light" version of get_buffer to the class, like this

//------------------------------------------------------------------------
function get_raw_buffer(){
    return $this->buffer;

}

and do the necessary trimming/searching in the result yourself.

You might also want to add the following constant

define ("TELNET_EOF", 3);

and change read_to like this

...
if ($c === false){
    // plus de caracteres a lire sur la socket
    if ($this->contientErreur($buf)){
        return TELNET_EOF;
    }

    $this->error = " Couldn't find the requested : '" . $chaine . "', it was not in the data returned from server : '" . $buf . "'" ;
    $this->logger($this->error);
    return TELNET_EOF;
} 
...

in order to treat that special case yourself (a result code TELNET_EOF doesn't have to be treated as an error in your case). So finally your code should look more or less like this:

// read to \n or whatever terminates the string you need to read 
if ($telnet->read_to("\n") == TELNET_ERROR) {  
    printf("Telnet error on read_to, %s\n",$telnet->get_last_error()); } echo "3<br>";
} else {
    $result = $telnet->get_raw_buffer();
    echo $result;
    print_r($result);
}