如何判断FTp是否连接成功？

[weixin_38055888]

int QFtp::connectToHost ( const QString & host, quint16 port = 21 )The function does not block and returns immediately. The command is scheduled, and its execution is performed asynchronously. The function returns a unique identifier which is passed by commandStarted() and commandFinished().是说id不会马上return回来么？那我怎么判断是否连接成功了？而且就是返回了那我得到什么样的数算是连接成功了呢？

[山鸟同学]

抓包 三次握手啊