Note that most *Async methods (with corresponding *Completed events) are using the Event-Based Asynchronous Pattern.
The older (but still perfectly valid) Begin* and End* is a pattern called the Asynchronous Programming Model.
已经推荐使用 await _ConnectStream.ReadAsync(_readBuffer, 0, _readBuffer.Length);
代替 _ConnectStream.beginRead(XXXX);
