php来实现telnet的连接、传递命令、获取返回值等功能！

<?php
error_reporting(-1);
  
class Telnet {
 var $sock = NULL;
   
 function telnet($host,$port) {
  $this->sock = fsockopen($host,$port);
  socket_set_timeout($this->sock,2,0);
 }
  
 function close() {
  if ($this->sock)  fclose($this->sock);
  $this->sock = NULL;
 }
   
 function write($buffer) {
  $buffer = str_replace(chr(255),chr(255).chr(255),$buffer);
  fwrite($this->sock,$buffer);
 }
   
 function getc() {
  return fgetc($this->sock);
 }
  
 function read_till($what) {
  $buf = &#39;&#39;;
  while (1) {
   $IAC = chr(255);
     
   $DONT = chr(254);
   $DO = chr(253);
     
   $WONT = chr(252);
   $WILL = chr(251);
     
   $theNULL = chr(0);
   
   $c = $this->getc();
     
   if ($c === false) return $buf;
   if ($c == $theNULL) {
    continue;
   }
   
   if ($c == "1") {
    continue;
   }
  
   if ($c != $IAC) {
    $buf .= $c;
    
    if ($what == (substr($buf,strlen($buf)-strlen($what)))) {
     return $buf;
    }
    else {
     continue;
    }
   }
  
   $c = $this->getc();
     
   if ($c == $IAC) {
   $buf .= $c;
   }
   else if (($c == $DO) || ($c == $DONT)) {
    $opt = $this->getc();
    // echo "we wont ".ord($opt)."\n";
    fwrite($this->sock,$IAC.$WONT.$opt);
   }
   elseif (($c == $WILL) || ($c == $WONT)) {
    $opt = $this->getc();
    // echo "we dont ".ord($opt)."\n";
    fwrite($this->sock,$IAC.$DONT.$opt);
   }
   else {
    // echo "where are we? c=".ord($c)."\n";
   }
  }
 }
}
  
/*
$telnet = new telnet("192.168.0.1",23);
echo $telnet->read_till("login: ");
$telnet->write("kongxx\r\n");
echo $telnet->read_till("password: ");
$telnet->write("KONGXX\r\n");
echo $telnet->read_till(":> ");
$telnet->write("ls\r\n");
echo $telnet->read_till(":> ");
echo $telnet->close();
  
*/