What are the serial Programming Problems in linux ???

What are the serial Programming Problems in linux ??? -- Linux general technology-Linux programming and kernel information. The following is a detailed description. In recent days, I learned serial programming and wrote code according to the tutorial in the book. During the test, it was okay to send data to the serial port through the write function (I have two comports on my machine, the system is XP, and virtualora 10 is installed with VirtualBox, and the data sent by fedora is received through the XP Terminal Service). However, when I use the read function to receive data, only garbled characters are received, and there is no waiting. As long as a compiled document is executed, the code runs directly and a garbled string is returned. I really don't understand what is going on here. I posted the code. Please help me to see if I was wrong. Thank you.

# Include
# Include
# Include
# Include
# Include
# Include
# Include
# Include
# Include


Int fd;


Struct termio
{
Unsigned short c_iflag;
Unsigned short c_oflag;
Unsigned short c_cflag;
Unsigned short c_lflag;
Unsigned char c_line;
Unsigned char c_cc [NCCS];

};


Int open_port (int comport)
{
If (comport = 1)
{
Fd = open ("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY );
If (fd =-1)
{
Perror ("Can't Open Serial Port ");
Return (-1 );
}
}
Else if (comport = 2)
{
Fd = open ("/dev/ttyS1", O_RDWR | O_NOCTTY | O_NDELAY );
If (fd =-1)
{
Perror ("Can't Open Serial Port ");
Return (-1 );
}
}
Else if (comport = 3)
{
Fd = open ("/dev/ttyS2", O_RDWR | O_NOCTTY | O_NDELAY );
If (fd =-1)
{
Perror ("Can't Open Serial Port ");
Return (-1 );
}
}



If (fcntl (fd, F_SETFL, 0) <0)
Printf ("fcntl failed! \ N ");
Else
Printf ("fcntl = % d \ n", fcntl (fd, F_SETFL, 0 ));

If (isatty (STDIN_FILENO) = 0)
Printf ("standard input is not a terminal device \ n ");
Else
Printf ("isatty success! \ N ");

Printf ("fd-open = % d \ n", fd );
Return fd;

}



Int set_opt (int fd, int nSpeed, int nBits, char nEvent, int nStop )//
{
Struct termios newtio, oldtio;
If (tcgetattr (fd, & oldtio )! = 0)
{
Perror ("SetupSerial 1 ");
Return-1;
}
Bzero (& newtio, sizeof (newtio ));
//
Newtio. c_cflag | = CLOCAL | CREAD;
Newtio. c_cflag & = ~ CSIZE;
//
Switch (nBits)
{
Case 7:
Newtio. c_cflag | = CS7;
Break;
Case 8:
Newtio. c_cflag | = CS8;
Break;
}
//
Switch (nEvent)
{
Case 'O ':
Newtio. c_cflag | = PARENB;
Newtio. c_cflag | = PARODD;
Newtio. c_iflag | = (INPCK | ISTRIP );
Break;
Case 'E ':
Newtio. c_iflag | = (INPCK | ISTRIP );
Newtio. c_cflag | = PARENB;
Newtio. c_cflag & = ~ PARODD;
Break;
Case 'N ':
Newtio. c_cflag & = ~ PARENB;
Break;
}
//
Switch (nSpeed)
{
Case 2400:
Cfsetispeed (& newtio, B2400 );
Cfsetospeed (& newtio, B2400 );
Break;
Case 4800:
Cfsetispeed (& newtio, B4800 );
Cfsetospeed (& newtio, B4800 );
Break;
Case 9600:
Cfsetispeed (& newtio, B9600 );
Cfsetospeed (& newtio, B9600 );
Break;
Case 115200:
Cfsetispeed (& newtio, B115200 );
Cfsetospeed (& newtio, B115200 );
Break;
Case 460800:
Cfsetispeed (& newtio, B460800 );
Cfsetospeed (& newtio, B460800 );
Break;
Default:
Cfsetispeed (& newtio, B9600 );
Cfsetospeed (& newtio, B9600 );
Break;
}
//
If (nStop = 1)
Newtio. c_cflag & = ~ CSTOPB;
Else if (nStop = 2)
Newtio. c_cflag | = CSTOPB;
//
Newtio. c_cc [VTIME] = 0;
Newtio. c_cc [VMIN] = 0;
//
Tcflush (fd, TCIFLUSH );
//
If (tcsetattr (fd, TCSANOW, & newtio ))! = 0)
{
Perror ("com set error ");
Return-1;
}
Printf ("set done! \ N ");
Return 0;
}



Int main ()
{
Int I, j;
Char na [30];
Fd = open_port (1 );
Printf ("fd = % d \ n", fd );
J = set_opt (fd, 115200,8, 'n', 1 );
Printf ("j = % d \ n", j );
I = read (fd, na, 31 );
Printf ("I = % d, na = % s \ n", I, na );
Close (fd );
Return;
}

[ This post was last edited at, 657371]