谁能告诉我第二个do循环不能执行，第一个do为什么跳不出来啊

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <string.h>
#define BUFFER_SIZE 512
#define TRUE 1
#define FALSE 0
#define COM1 "/dev/s3c2410_serial1"
int speed_arr[] = { B38400, B19200, B9600, B4800, B2400, B1200, B300,
B38400, B19200, B9600, B4800, B2400, B1200, B300, };
int name_arr[] = { 38400, 19200, 9600, 4800, 2400, 1200, 300,
38400, 19200, 9600, 4800, 2400, 1200, 300, };
void set_speed(int fd, int speed)
{
int i;
int status;
struct termios Opt;
tcgetattr(fd, &Opt);
for ( i= 0; i < sizeof(speed_arr) / sizeof(int); i++)
{
if (speed == name_arr[i])
{
tcflush(fd, TCIOFLUSH);
cfsetispeed(&Opt, speed_arr[i]);
cfsetospeed(&Opt, speed_arr[i]);
status = tcsetattr(fd, TCSANOW, &Opt);
if (status != 0)
perror("tcsetattr fd1");
return;
}
tcflush(fd,TCIOFLUSH);
}
}
int set_Parity(int fd,int databits,int stopbits,int parity)
{
struct termios options;
if ( tcgetattr( fd,&options) != 0)
{
perror("SetupSerial 1");
return(FALSE);
}
options.c_cflag &= ~CSIZE;
switch (databits)
{
case 7:
options.c_cflag |= CS7;
break;
case 8:
options.c_cflag |= CS8;
break;
default:
fprintf(stderr,"Unsupported data size\n");
return (FALSE);
}
switch (parity)
{
case *n*:
case *N*:
options.c_cflag &= ~PARENB; /* Clear parity enable */
options.c_iflag &= ~INPCK; /* Enable parity checking */
break;
case *o*:
case *O*:
options.c_cflag |= (PARODD | PARENB);
options.c_iflag |= INPCK; /* Disnable parity checking */
break;
case *e*:
case *E*:
options.c_cflag |= PARENB; /* Enable parity */
options.c_cflag &= ~PARODD;
options.c_iflag |= INPCK; /* Disnable parity checking */
break;
case *S*:
case *s*: /*as no parity*/
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
break;
default:
fprintf(stderr,"Unsupported parity\n");
return (FALSE);
}
switch (stopbits)
{
case 1:
options.c_cflag &= ~CSTOPB;
break;
case 2:
options.c_cflag |= CSTOPB;
break;
default:
fprintf(stderr,"Unsupported stop bits\n");
return (FALSE);
}
/* Set input parity option */
if (parity != *n*)
options.c_iflag |= INPCK;
options.c_cc[VTIME] = 150; // 15 seconds
options.c_cc[VMIN] = 0;
tcflush(fd,TCIFLUSH); /* Update the options and do it NOW */
if (tcsetattr(fd,TCSANOW,&options) != 0)
{
perror("SetupSerial 3");
return (FALSE);
}
return (TRUE);
}
int OpenDev(char *Dev)
{
intfd = open( Dev, O_RDWR ); //| O_NOCTTY | O_NDELAY
if (-1 == fd)
{
perror("Can*t Open Serial Port");
return -1;
}
else
return fd;
}
/**
*@breif main()
*/
int main(int argc, char **argv)
{
int fd;
int nwrite;
int nread;
int len;
char buff[512];
char *dev ="/dev/s3c2410_serial1";
fd = OpenDev(dev);
//printf("please enter any data to the ttyS0, Enter key to confirm\n");
set_speed(fd,115200);
if (set_Parity(fd,8,1,*N*)== FALSE)
{
printf("Set Parity Error\n");
exit(1);
}
do
{
printf(" input some words:");
memset(buff,0,BUFFER_SIZE);
if(fgets(buff,BUFFER_SIZE,stdin)==NULL)
{
}
perror("fgets");break;
write(fd,buff,strlen(buff));
}
while(strncmp(buff,"quit",4));
do
{
memset(buff,0,BUFFER_SIZE);
if(read(fd,buff,BUFFER_SIZE)>0)
{
}}while(strncmp(buff,"quit",4)==0);
printf("the received words are: %s",buff);
close(fd);
}