SerialPort 读取数据被分片的问题 麻烦看清楚在关我的issues

[sitapandery]

Description

在串口读取中假设串口设备发送了75个字节，但是在大部分情况下 SerialPort.Read中会收到两次 一次可能40多个字节 一次30多个字节

Reproduction Steps

接上ttl 往串口发送75个字节的数据 波特率设置为115200，然后就可以复现
代码

using System;
using System.IO.Ports;

namespace ConsoleApp1
{
    internal class Program
    {
        private static SerialPort _serialPort;

        static void Main(string[] args)
        {
            // 初始化串口
            _serialPort = new SerialPort("COM3", 115200);
            _serialPort.DataReceived += SerialPort_DataReceived;
            _serialPort.Open();

            Console.WriteLine("串口已打开，等待数据...");
            Console.ReadLine();

            _serialPort.Close();
        }

        private static void SerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            try
            {
                // 读取串口数据
                int bytesToRead = _serialPort.BytesToRead;
                byte[] buffer = new byte[bytesToRead];
                _serialPort.Read(buffer, 0, bytesToRead);

                // 输出数据长度和十六进制表示
                Console.WriteLine($"接收到 {buffer.Length} 个字节: {BitConverter.ToString(buffer)}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"数据接收错误: {ex.Message}");
            }
        }
    }
}

此代码结果

直接使用底层api的代码

using System;
using System.IO;
using System.Runtime.InteropServices;
using Microsoft.VisualBasic;
using Microsoft.Win32.SafeHandles;

namespace ConsoleApp18
{
    internal class Program
    {
        // Windows API 常量
        private const uint GENERIC_READ = 0x80000000;
        private const uint GENERIC_WRITE = 0x40000000;
        private const uint OPEN_EXISTING = 3;

        // DCB 结构体，用于配置串口参数
        [StructLayout(LayoutKind.Sequential)]
        private struct DCB
        {
            public uint DCBlength;
            public uint BaudRate;
            public uint Flags;
            public ushort wReserved;
            public ushort XonLim;
            public ushort XoffLim;
            public byte ByteSize;
            public byte Parity;
            public byte StopBits;
            public byte XonChar;
            public byte XoffChar;
            public byte ErrorChar;
            public byte EofChar;
            public byte EvtChar;
            public ushort wReserved1;
        }

        // COMMTIMEOUTS 结构体，用于设置超时
        [StructLayout(LayoutKind.Sequential)]
        private struct COMMTIMEOUTS
        {
            public int ReadIntervalTimeout;
            public int ReadTotalTimeoutMultiplier;
            public int ReadTotalTimeoutConstant;
            public uint WriteTotalTimeoutMultiplier;
            public uint WriteTotalTimeoutConstant;
        }

        // Windows API 函数声明
        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern IntPtr CreateFile(
            string lpFileName,
            uint dwDesiredAccess,
            uint dwShareMode,
            IntPtr lpSecurityAttributes,
            uint dwCreationDisposition,
            uint dwFlagsAndAttributes,
            IntPtr hTemplateFile);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern bool GetCommState(IntPtr hFile, ref DCB lpDCB);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern bool SetCommState(IntPtr hFile, [In] ref DCB lpDCB);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern bool SetCommTimeouts(IntPtr hFile, [In] ref COMMTIMEOUTS lpCommTimeouts);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern bool CloseHandle(IntPtr hObject);

        static void Main(string[] args)
        {
            string portName = "COM5"; // 替换为实际的串口名称
            System.IO.FileStream stream=new FileStream($"\\\\.\\{portName}", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
            if (stream == null)
            {
                Console.WriteLine("无法打开串口。");
                return;
            }
            IntPtr hSerial = stream.Handle;
            if (hSerial == IntPtr.Zero)
            {
                Console.WriteLine("无法打开串口。");
                return;
            }

            try
            {
                // 配置串口参数
                DCB dcb = new DCB();
                dcb.DCBlength = (uint)Marshal.SizeOf(typeof(DCB));
                dcb.BaudRate = 115200; // 设置波特率
                dcb.ByteSize = 8; // 数据位
                dcb.Parity = 0; // 无校验
                dcb.StopBits = 1; // 1 个停止位

                if (!SetCommState(hSerial, ref dcb))
                {
                    int errorCode = Marshal.GetLastWin32Error();
                    Console.WriteLine($"设置串口状态失败，错误代码: {errorCode}");
                  //  return;
                }

                // 设置超时
                COMMTIMEOUTS timeouts = new COMMTIMEOUTS
                {
                    ReadIntervalTimeout = 50,//非常重要
                    ReadTotalTimeoutConstant = 50,
                    ReadTotalTimeoutMultiplier = 100,
                    WriteTotalTimeoutConstant = 50,
                    WriteTotalTimeoutMultiplier = 10
                };

                if (!SetCommTimeouts(hSerial, ref timeouts))
                {
                    Console.WriteLine("设置超时失败。");
                    return;
                }

                // 将句柄包装为 SafeFileHandle
                SafeFileHandle safeHandle = new SafeFileHandle(hSerial, ownsHandle: true);

                // 使用 FileStream 包装 SafeFileHandle
                {
                    Console.WriteLine("串口已打开，开始读取数据...");

                    byte[] buffer = new byte[256];
                    while (true)
                    {
                        int bytesRead = stream.Read(buffer, 0, buffer.Length);
                        if (bytesRead > 0)
                        {
                            string data = BitConverter.ToString(buffer, 0, bytesRead);
                            Console.WriteLine($"接收到数据: {data}");
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"发生错误: {ex.Message}");
            }
            finally
            {
                // 确保关闭句柄
                CloseHandle(hSerial);
                Console.WriteLine("串口已关闭。");
            }
        }
    }
}

此代码结果

Expected behavior

希望能一次性读到对方发送的完整数据

Actual behavior

实际上收到的被拆包了

Regression?

已知的所有版本都有这个问题，

Regression?

windows的解决方案我找到了,就是SetCommTimeouts的ReadIntervalTimeout默认为-1的原因导致的，如果设置成50 就不会出现这个问题，在源码中的https://github.com/dotnet/runtime/blob/main/src/libraries/System.IO.Ports/src/System/IO/Ports/SerialStream.Windows.cs 的第373行 _commTimeouts.ReadIntervalTimeout = Interop.Kernel32.MAXDWORD; 这里将ReadIntervalTimeout值设置为了-1，建议将次参数作为属性放出来，liunx中也有此问题，但是我未找到修复方案，ai告知我也有类似的参数，建议也放出来，或者放出来串口的句柄，让开发人员有渠道去手动设置。

Known Workarounds

.net 全版本
系统 windows10 11、liunx arm32 arm64 其它系统未测试

Configuration

No response

Other information

No response

[sitapandery]

问题 的回答不正确 重新提交，

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-io-ports
See info in area-owners.md if you want to be subscribed.

[huoyaoyuan]

请在原issue继续进行讨论，close后仍可继续讨论，并在需要时reopen。