fsockopen - PHP code example

PHP Function fsockopen - Syntax and Usage

In some situations, you may need to establish network connections and send/receive data through them. In such cases, php function fsockopen can come in handy as it’s a powerful tool for creating network socket connections. This article will take a look at the syntax and usage of this built-in function in PHP.

Sockets are channels through which different protocols (methods of communication) pass on a server. When using fsockopen, you open a socket by providing a URL, the port on which the protocol will run (here, 80), an error number variable, and an error string variable. The fsockopen() function then returns a file pointer that can be used with other file functions such as fgets, fwrite and fclose.

For example, in a simple script, you can use the fsockopen() function to connect to a webserver and perform a HTTP request on it. The result would be similar to that of the file_get_contents() function in PHP except that you would receive all of the HTTP headers sent by the webserver.

The fsockopen() function can also be used to initiate a socket connection with SSL/TLS support. To do so, you must prefix the hostname with ‘ssl://’ or 'tls://'.

Note that fsockopen() is dangerous in the sense that it can be used by an attacker to open sockets and execute code on your server. However, this can be mitigated by enabling the ASL ASL plugin and using the PHP_CHECKS option in ASL to check for PHP vulnerabilities such as remote inclusion and shells.

fsockopen example

$timeout,
                STREAM_CLIENT_CONNECT,
                $socket_context
            );
        } else {
            //Fall back to fsockopen which should work in more places, but is missing some features             $this->edebug(
                'Connection: stream_socket_client not available, falling back to fsockopen',
                self::DEBUG_CONNECTION
            );
            set_error_handler([$this, 'errorHandler']);
            $connection = fsockopen(
                $host,
                $port,
                $errno,
                $errstr,
                $timeout
            );
        }
        restore_error_handler();

        //Verify we connected properly         if (!is_resource($connection)) {

$url_parts = parse_url($url);
                $socket_host = $url_parts['host'];
                if (isset($url_parts['scheme']) && strtolower($url_parts['scheme']) === 'https')
                {
                    $socket_host = "ssl://$url_parts[host]";
                    $url_parts['port'] = 443;
                }
                if (!isset($url_parts['port']))
                {
                    $url_parts['port'] = 80;
                }
                $fp = @fsockopen($socket_host, $url_parts['port'], $errno, $errstr, $timeout);
                if (!$fp)
                {
                    $this->error = 'fsockopen error: ' . $errstr;
                    $this->success = false;
                }
                else
                {
                    stream_set_timeout($fp, $timeout);
                    if (isset($url_parts['path']))
                    {
                        if (isset($url_parts['query']))
                        {

        if ($ssl == 'SSL') {
            $host = 'ssl://' . $host;
        }

        if ($port === null) {
            $port = $ssl === 'SSL' ? 993 : 143;
        }

        $errno  =  0;
        $errstr = '';
        $this->_socket = @fsockopen($host, $port, $errno, $errstr, self::TIMEOUT_CONNECTION);
        if (!$this->_socket) {
            /** * @see Zend_Mail_Protocol_Exception */
            throw new Zend_Mail_Protocol_Exception('cannot connect to host; error = ' . $errstr .
                                                   ' (errno = ' . $errno . ' )');
        }

        if (!$this->_assumedNextLine('* OK')) {
            /** * @see Zend_Mail_Protocol_Exception */

  protected function findAvailablePort($host) {
    $port = 8888;
    while ($port >= 8888 && $port <= 9999) {
      $connection = @fsockopen($host, $port);
      if (is_resource($connection)) {
        // Port is being used.         fclose($connection);
      }
      else {
        // Port is available.         return $port;
      }
      $port++;
    }
    return FALSE;
  }

$host = $this->proxy_host;
                $port = $this->proxy_port;
            }
        else
        {
            $host = $this->host;
            $port = $this->port;
        }

        $this->status = 0;

        if($fp = fsockopen(
                    $host,
                    $port,
                    $errno,
                    $errstr,
                    $this->_fp_timeout
                    ))
        {
            // socket connection succeeded
            return true;
        }

        $request .= $r;

        $request .= $xml;

        // Now send the request         if ($this->debug) {
            echo '<pre class="ixr_request">'.htmlspecialchars($request)."\n</pre>\n\n";
        }

        if ($this->timeout) {
            $fp = @fsockopen($this->server, $this->port, $errno, $errstr, $this->timeout);
        } else {
            $fp = @fsockopen($this->server, $this->port, $errno, $errstr);
        }
        if (!$fp) {
            $this->error = new IXR_Error(-32300, 'transport error - could not open socket');
            return false;
        }
        fputs($fp, $request);
        $contents = '';
        $debugContents = '';
        $gotFirstLine = false;

    if (!isset($port) || !$port) {$port = 110;}
        if(!empty($this->MAILSERVER))
            $server = $this->MAILSERVER;

        if(empty($server)){
            $this->ERROR = "POP3 connect: " . _("No server specified");
            unset($this->FP);
            return false;
        }

        $fp = @fsockopen("$server", $port, $errno, $errstr);

        if(!$fp) {
            $this->ERROR = "POP3 connect: " . _("Error ") . "[$errno] [$errstr]";
            unset($this->FP);
            return false;
        }

        socket_set_blocking($fp,-1);
        $this->update_timer();
        $reply = fgets($fp,$this->BUFFER);
        $reply = $this->strip_clf($reply);

trigger_error("[plugin] invalid value for attribute '".$param_key."'",E_USER_NOTICE);
                            return;
                        }
                        break;
                    default:
                        trigger_error("[plugin] unrecognized attribute '".$param_key."'",E_USER_NOTICE);
                        return;
                }
            }
            if(!empty($proxy_host) && !empty($proxy_port)) {
                $_is_proxy = true;
                $fp = fsockopen($proxy_host,$proxy_port,$errno,$errstr,$timeout);
            } else {
                $fp = fsockopen($server_name,$port,$errno,$errstr,$timeout);
            }

            if(!$fp) {
                trigger_error("[plugin] unable to fetch: $errstr ($errno)",E_USER_NOTICE);
                return;
            } else {
                if($_is_proxy) {
                    fputs($fp, 'GET ' . $params['file'] . " HTTP/1.0\r\n");
                } else {

  /** * Checks whether a port is available. * * @param $port * A number between 1024 and 65536. * * @return bool */
  protected function checkPortIsAvailable($port) {
    $fp = @fsockopen(self::$hostName, $port, $errno, $errstr, 1);
    // If fsockopen() fails to connect, probably nothing is listening.     // It could be a firewall but that's impossible to detect, so as a     // best guess let's return it as available.     if ($fp === FALSE) {
      return TRUE;
    }
    else {
      fclose($fp);
    }
    return FALSE;
  }

function _settimeout($sock) {
        if(!@stream_set_timeout($sock, $this->_timeout)) {
            $this->PushError('_settimeout','socket set send timeout');
            $this->_quit();
            return FALSE;
        }
        return TRUE;
    }

    function _connect($host, $port) {
        $this->SendMSG("Creating socket");
        $sock = @fsockopen($host, $port, $errno, $errstr, $this->_timeout);
        if (!$sock) {
            $this->PushError('_connect','socket connect failed', $errstr." (".$errno.")");
            return FALSE;
        }
        $this->_connected=true;
        return $sock;
    }

    function _readmsg($fnction="_readmsg"){
        if(!$this->_connected) {
            $this->PushError($fnction, 'Connect first');

// Connection to port 465 should use implicit TLS (without STARTTLS)         // as per RFC 8314.         if ($this->SMTPPort === 465) {
            $ssl = 'tls://';
        }
        // But if $SMTPCrypto is set to `ssl`, SSL can be used.         if ($this->SMTPCrypto === 'ssl') {
            $ssl = 'ssl://';
        }

        $this->SMTPConnect = fsockopen(
            $ssl . $this->SMTPHost,
            $this->SMTPPort,
            $errno,
            $errstr,
            $this->SMTPTimeout
        );

        if (! is_resource($this->SMTPConnect)) {
            $this->setErrorMessage(lang('Email.SMTPError', [$errno . ' ' . $errstr]));

            return false;
        }

        if ($ssl == 'SSL') {
            $host = 'ssl://' . $host;
        }

        if ($port === null) {
            $port = $ssl == 'SSL' ? 995 : 110;
        }

        $errno  =  0;
        $errstr = '';
        $this->_socket = @fsockopen($host, $port, $errno, $errstr, self::TIMEOUT_CONNECTION);
        if (!$this->_socket) {
            /** * @see Zend_Mail_Protocol_Exception */
            throw new Zend_Mail_Protocol_Exception('cannot connect to host; error = ' . $errstr .
                                                   ' (errno = ' . $errno . ' )');
        }

        $welcome = $this->readResponse();

        strtok($welcome, '<');