Merge branch '3.0-isconnected-tweak' into 3.0

phpseclib/Net/SSH2.php

@@ -3344,11 +3344,38 @@ public function __destruct()
     /**
      * Is the connection still active?
      *
+     * $level has 3x possible values:
+     * 0 (default): phpseclib takes a passive approach to see if the connection is still active by calling feof()
+     *    on the socket
+     * 1: phpseclib takes an active approach to see if the connection is still active by sending an SSH_MSG_IGNORE
+     *    packet that doesn't require a response
+     * 2: phpseclib takes an active approach to see if the connection is still active by sending an SSH_MSG_CHANNEL_OPEN
+     *    packet and imediately trying to close that channel. some routers, in particular, however, will only let you
+     *    open one channel, so this approach could yield false positives
+     *
+     * @param int $level
      * @return bool
      */
-    public function isConnected()
+    public function isConnected($level = 0)
     {
-        return ($this->bitmap & self::MASK_CONNECTED) && is_resource($this->fsock) && !feof($this->fsock);
+        if (!is_int($level) || $level < 0 || $level > 2) {
+            throw new \InvalidArgumentException('$level must be 0, 1 or 2');
+        }
+
+        if ($level == 0) {
+            return ($this->bitmap & self::MASK_CONNECTED) && is_resource($this->fsock) && !feof($this->fsock);
+        }
+        try {
+            if ($level == 1) {
+                $this->send_binary_packet(pack('CN', NET_SSH2_MSG_IGNORE, 0));
+            } else {
+                $this->openChannel(self::CHANNEL_KEEP_ALIVE);
+                $this->close_channel(self::CHANNEL_KEEP_ALIVE);
+            }
+            return true;
+        } catch (\Exception $e) {
+            return false;
+        }
     }
 
     /**