AsyncTcpConnection 异步tcp连接类

 $this->_socket = stream_socket_client("tcp://{$this->_remoteAddress}", $errno, $errstr, 0, STREAM_CLIENT_ASYNC_CONNECT);

// 创建异步连接
$this->_socket = stream_socket_client("tcp://{$this->_remoteAddress}", $errno, $errstr, 0, STREAM_CLIENT_ASYNC_CONNECT);
// 如果失败尝试触发失败回调（如果有回调的话）
if(!$this->_socket)
{
    $this->_status = self::STATUS_CLOSED;
    $this->emitError(WORKERMAN_CONNECT_FAIL, $errstr);
    return;
}
// 监听连接可写事件（可写意味着连接已经建立或者已经出错）
Worker::$globalEvent->add($this->_socket, EventInterface::EV_WRITE, array($this, 'checkConnection'));