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neelc20 11-28-2003 04:44 AM

Detecting connection break on serial port listener on linux

Can anyone let me know how to detect the client connection break on a serial port listener on linux?
I have written an application that opens the serial port and is able to read and write data. My serial port listener is running on Linux and I am using HyperTerminal (WIN-NT/2K) for communication on client side.

The problem: Now when I DISCONNECT the client from the CALL menu in HyperTerminal, I am not able to detect the disconnection at the listener. Here is my sample piece of code. Please suggest something, if you have any idea or working on it.

Thanking you in advance.

Sample code follows:

#include <stdio.h> /* Standard input/output definitions */
#include <string.h> /* String function definitions */
#include <unistd.h> /* UNIX standard function definitions */
#include <fcntl.h> /* File control definitions */
#include <errno.h> /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

int main()
// open serial port for communication
int serialFd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY );
if (fd == -1)
//printf("Could not open the port\n\n");
perror("open_port: Unable to open /dev/ttyS0 - ");
fcntl(fd, F_SETFL, 0);

struct termios options;

//get the port options
tcgetattr(serialFd, &options);

cfsetispeed(&options, B9600);
cfsetospeed(&options, B9600);
options.c_cflag |= (CLOCAL | CREAD);

// setting for 8bits, No parity, 1 Stop bit
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;

// choosing raw input
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
// ignore input parity check
options.c_lflag &= ~INPCK;
// check parity errors and strip parity bits
options.c_lflag |= (IGNPAR | ISTRIP);
//diabling software flow control
options.c_lflag &= ~(IXON | IXOFF | IXANY);
// choosing processed output and map NL to CR-NL
options.c_lflag |= (OPOST | ONLCR);

// set the configured options of the port
tcsetattr(serialFd, TCSANOW, &options);

// set port mode to no delay
fcntl(serialFd, F_SETFL, FNDELAY);

write(serialFd, "Welcome to PORT COM1", 20 ) ;

int flag = 0;
char buf[256];
memset(buf, 0, 256);
while (flag == false) /* loop for input */
int res = read(serialFd, buf, 255);
write(fd, "Buffer read :%s\n", buf);
if (buf[0]=='z')
flag = true;
return 0;

Joey.Dale 11-28-2003 01:56 PM

please don't post the same thread in more than one fourm see the rules

david_ross 11-29-2003 11:22 AM

Please do not post the same thread in more than one forum. Picking the most relevant forum and posting it once there makes it easier for other members to help you and keeps the discussion all in one place.

The original is here:

Mara 11-29-2003 03:29 PM

I'm closing this thread, please post all replies to

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