boost::asio::serial_port bug in win10

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在最近写一些串口操作的程序时使用了 boost::asio::serial_port 来操作串口 但当尝试打开串口的时候出现了错误。下面是我的测试代码：

boost::asio::io_service _io_service;
const std::string devname = "COM3";
try
{
        boost::asio::serial_port serial(_io_service);
        serial.open(devname);// throw error every times.
        if (serial.is_open()) {
                std::cout << devname << " serial open successed." << std::endl;
        }
        else {
                std::cout << devname << " serial open failed!" << std::endl;
        }
}
catch (const std::exception& ex)
{
        std::cout << ex.what() << std::endl;// GetLastError() == 87
}

每次都会出现错误87。即 GetLastError() 的结果为 87 于是跟进代码里面调试追到了 win_iocp_serial_port_service::open 函数里

win_iocp_serial_port_service::open 函数的实现如下：

boost::system::error_code win_iocp_serial_port_service::open(
        win_iocp_serial_port_service::implementation_type& impl,
        const std::string& device, boost::system::error_code& ec)
{
        if (is_open(impl))
        {
                ec = boost::asio::error::already_open;
                return ec;
        }

        std::string name = (device[0] == '\\') ? device : "\\\\.\\" + device;

        ::HANDLE handle = ::CreateFileA(name.c_str(),
                GENERIC_READ | GENERIC_WRITE, 0, 0,
                OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
        if (handle == INVALID_HANDLE_VALUE)
        {
                DWORD last_error = ::GetLastError();
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        using namespace std;
        ::DCB dcb;
        memset(&dcb, 0, sizeof(DCB));
        dcb.DCBlength = sizeof(DCB);
        if (!::GetCommState(handle, &dcb))
        {
                DWORD last_error = ::GetLastError();
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        dcb.fBinary = TRUE;
        dcb.fDsrSensitivity = FALSE;
        dcb.fNull = FALSE;
        dcb.fAbortOnError = FALSE;

        if (!::SetCommState(handle, &dcb))
        {
                DWORD last_error = ::GetLastError();// lee: error is here!!!
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        ::COMMTIMEOUTS timeouts;
        timeouts.ReadIntervalTimeout = 1;
        timeouts.ReadTotalTimeoutMultiplier = 0;
        timeouts.ReadTotalTimeoutConstant = 0;
        timeouts.WriteTotalTimeoutMultiplier = 0;
        timeouts.WriteTotalTimeoutConstant = 0;
        if (!::SetCommTimeouts(handle, &timeouts))
        {
                DWORD last_error = ::GetLastError();
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        if (handle_service_.assign(impl, handle, ec))
                ::CloseHandle(handle);
        return ec;
}

发现每次在第一次 SetCommState 的时候总是会报错并离开。 于是查看了前面通过 GetCommState 获取到的 dcb 的值。 发现 dcb.BaudRate == 0 时无法 SetCommState 成功 也就是说在有些设备中获取不到 dcb.BaudRate 这个值。

下面是我自己的解决办法：

在 win_iocp_serial_port_service.ipp 文件的88行左右添加

if (dcb.BaudRate == 0) dcb.BaudRate = 115200;

修改后的 win_iocp_serial_port_service::open 函数完整代码如下：

boost::system::error_code win_iocp_serial_port_service::open(
        win_iocp_serial_port_service::implementation_type& impl,
        const std::string& device, boost::system::error_code& ec)
{
        if (is_open(impl))
        {
                ec = boost::asio::error::already_open;
                return ec;
        }

        std::string name = (device[0] == '\\') ? device : "\\\\.\\" + device;

        ::HANDLE handle = ::CreateFileA(name.c_str(),
                GENERIC_READ | GENERIC_WRITE, 0, 0,
                OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
        if (handle == INVALID_HANDLE_VALUE)
        {
                DWORD last_error = ::GetLastError();
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        using namespace std;
        ::DCB dcb;
        memset(&dcb, 0, sizeof(DCB));
        dcb.DCBlength = sizeof(DCB);
        if (!::GetCommState(handle, &dcb))
        {
                DWORD last_error = ::GetLastError();
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        dcb.fBinary = TRUE;
        dcb.fDsrSensitivity = FALSE;
        dcb.fNull = FALSE;
        dcb.fAbortOnError = FALSE;
        if (dcb.BaudRate == 0) dcb.BaudRate = 115200; // add lee 2015.10.10. 解决dcb.BaudRate为0时无法成功SetCommState的BUG
        if (!::SetCommState(handle, &dcb))
        {
                DWORD last_error = ::GetLastError();
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        ::COMMTIMEOUTS timeouts;
        timeouts.ReadIntervalTimeout = 1;
        timeouts.ReadTotalTimeoutMultiplier = 0;
        timeouts.ReadTotalTimeoutConstant = 0;
        timeouts.WriteTotalTimeoutMultiplier = 0;
        timeouts.WriteTotalTimeoutConstant = 0;
        if (!::SetCommTimeouts(handle, &timeouts))
        {
                DWORD last_error = ::GetLastError();
                ::CloseHandle(handle);
                ec = boost::system::error_code(last_error,
                        boost::asio::error::get_system_category());
                return ec;
        }

        if (handle_service_.assign(impl, handle, ec))
                ::CloseHandle(handle);
        return ec;
}

测试环境

说明	参数
操作系统	Windows10 专业版 x64
开发环境	Microsoft Visual Studio Community 2013 Version 12.0.40629.00 Update 5
Boost版本	boost_1.59.0

结束语

以上只是自己的猜测，并不一定是完全正确的。如有任何错误，请联系并告诉我。我将尽快修改，不胜感激。

我的原文

​http://www.leelib.com/2015/10/10/win10-boost-asio-serial-port-bug.html