从 Unix 中的串口读取时输入/输出错误

Question

My configurations for the serial port is close to the one in this link: Serial-programming-HOWTO in the non-canonical input mode. This is my code where the problem happens:

    char buffer;
    int received;

    while (true) {

        received = read(serial_com,
            &buffer,
            sizeof(buffer));


        if (received < 0) {
            
            perror("error reading") << endl;
            cout << "error no." << errno;
            //exit(1);
        }

        cout << buffer;
    }

After I read one character, sometimes it returns the read character, and other times it gives me this error:

error reading: Input/output error 
error no.5

This error occurs as soon as I run the program. How can I fix this?

I have also noticed that when I print the variable received , it first prints 0 and then prints -1 and then it prints the error mentioned.

Answer 1

Most likely you are trying to read data faster, than it comes in - and if you try to read a character, when none is available, this is indeed an IO error.

You have a few possibilities:

• Use blocking mode (this will freeze the program at the read() call, until data is available
• use select to make sure you only try to read, if there is a character available
• use a paltform-specific mechanism (like epoll )
• Use a library (like libev ) to abstract away these problems.