ModbusSerialPort.ReadByte（）读取超时问题
提示信息 Function evaluation timed out
之前 有 ModbusSerialPort.Write(message, 0, message.Length);操作 无异常
[解决办法]
http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/5825db89-0e7c-4353-973a-addfaee16333/
http://blogs.msdn.com/b/greggm/archive/2005/11/18/494648.aspx
