Serial Ports

    int fd = open("/dev/ttyS1", O_RDWR | O_NOCTTY | O_NDELAY);
    termios PortSettings;
    tcgetattr(fd,&PortSettings);

    PortSettings.c_cflag |= (CLOCAL | CREAD);          // Активируем приемник, разрешая чтение
    PortSettings.c_lflag |= ~(ICANON | ECHO | ECHOE | ISIG);
    PortSettings.c_oflag |= ~OPOST;
    PortSettings.c_iflag |= ~(IXON | IXOFF | IXANY);

    cfsetispeed(&PortSettings, B19200);
    cfsetospeed(&PortSettings, B19200);

    tcsetattr(fd,TCSANOW,&PortSettings);

    ssize_t TeakedByteCounter;
    size_t SendingByteCounter = 1;
    void *buff = NULL;

    fcntl(fd, F_SETFL, 0); // blocking on
    TeakedByteCounter = ::read(fd,buff,SendingByteCounter);

    ::close(fd);

    int fd = open("/dev/ttyS2", O_RDWR | O_NOCTTY | O_NDELAY);

    termios PortSettings;
    tcgetattr(fd,&PortSettings);
    PortSettings.c_cflag |= (CLOCAL | CREAD);
    PortSettings.c_lflag |= ~(ICANON | ECHO | ECHOE | ISIG);
    PortSettings.c_oflag |= ~OPOST;
    PortSettings.c_iflag |= ~(IXON | IXOFF | IXANY);

    cfsetispeed(&PortSettings, B19200);
    cfsetospeed(&PortSettings, B19200);

    tcsetattr(fd,TCSANOW,&PortSettings);

    ssize_t SendedByteCounter;
    SendedByteCounter = write(fd,"a",1);
    ::close(fd);

read(fd,buff,SendingByteCounter) == -1