.NET SerialPort写入/读取优化

Question

I've an UART device which I'm writing to it a command (via System.IO.Ports.SerialPort) and then immediately the device will respond.

So basically my approach is:

->Write to SerialPort->await Task.Delay->Read from the Port.

//The port is open all the time.
public async byte[] WriteAndRead(byte[] message){ 
port.Write(command, 0, command.Length);
await Task.Delay(timeout);
var msglen = port.BytesToRead;
    if (msglen > 0)
                {

                    byte[] message = new byte[msglen];
                    int readbytes = 0;

                    while (port.Read(message, readbytes, msglen - readbytes) <= 0)
                        ;

                    return message;

                    }

This works fine on my computer. But if I try it on another computer for example, the bytesToRead property is sometimes mismatched. There are empty bytes in it or the answer is not completed. (Eg I get two bytes, if I expect one byte: 0xBB, 0x00 or 0x00, 0xBB)

I've also looked into the SerialPort.DataReceived Event, but it fires too often and is (as far as I understand) not really useful for this write and read approach. (As I expect the answer immediately from the device).

Is there a better approach to a write-and-read?

Answer 1

Read carefully the Remarks in https://msdn.microsoft.com/en-us/library/ms143549(v=vs.110).aspx You should not rely on the BytesToRead value to indicate message length. You should know, how much data you expect to read to decompose the message. Also, as @itsme85 noticed, you are not updating the readbytes, and therefore you are always writing received bytes to beginning of your array. Proper code with updating the readbytes should look like this:

int r;
while ((r = port.Read(message, readbytes, msglen - readbytes)) <= 0){
  readbytes += r;
}

However, during the time you will read data, more data can come and your "message" might be incomplete. Rethink, what you want to achieve.