QSerialPort cannot open with error code 11 - c++

Question

I'm trying to communicate with a device which provided a serial port. When I use the example C program provided by the device producer, it was successfully connected and I can send/receive data. But when I use my C++ program with QSerialPort, the open() method returned false and the error() returned 11 (An unidentified error occurred, as described by Qt documentation). Could anyone please help me?
OS: Cent OS 6.9
gcc/g++: 4.8
Qt: 5.6.0
An example of connecting with QSerialPort:
#include <qserialport.h>
#include <qstring.h>
int main(int argc, const char *argv[])
{
QString portName = "/dev/corser/x64ExpCL4x1_s0";
QSerialPort *pSerial = new QSerialPort();
pSerial->setPortName(portName);
pSerial->setBaudRate(QSerialPort::Baud9600);
pSerial->setParity(QSerialPort::NoParity);
pSerial->setDataBits(QSerialPort::Data8);
pSerial->setStopBits(QSerialPort::OneStop);
pSerial->setFlowControl(QSerialPort::NoFlowControl);
bool success = pSerial->open(QIODevice::ReadWrite);
if (!success) {
printf("Error: %d\n", pSerial->error());
} else {
printf("Success.\n");
pSerial->close();
}
delete pSerial;
return 0;
}
This program prints out Error: 11.
Here is a C program which is excerpted from the device's example program. This program just try to connect the serial port and then close the connection. While the original example program is complicated. It is actually kind of a "Terminal" program which sends user-input commands to the device and prints out the responses from the device.
#include <unistd.h>
#include <termios.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <pthread.h>
#include <sys/ioctl.h>
#include <ctype.h> /* Character types */
#define TRUE 1
#define FALSE 0
typedef struct
{
int open; // Flag for current open status of port
int update; // Flag indicating parameter changes
char *port; // Current port to be opened
int iod; // I/O index for open device port
struct termios stty; // Terminal port control structure
} SCOM_CTL;
struct termios ttctl = {0};
struct termios ttsav = {0};
struct termios coctl = {0};
struct termios cnctl = {0};
#define OPEN 1
#define CLOSE 2
#define UPDATE 3
#define NO_UPDATE 4
SCOM_CTL scom;
int main( int argc, char **argv )
{
scom.port = "/dev/corser/x64ExpCL4x1_s0";
scom_init();
scom_open_port();
if (scom.open == OPEN)
{
fputs("\rSuccess.\r\n", stdout);
scom_close_port(scom.iod);
}
else
{
fputs("\rError.\r\n", stdout);
}
}
// Initialize the console (stdin) for raw access.
int scom_init()
{
int i;
scom.open = CLOSE;
scom.update = NO_UPDATE;
scom.iod = -1;
tcgetattr(0, &coctl); // Save a copy to restore stdin.
tcgetattr(0, &cnctl);
cfmakeraw( &cnctl); // Set stdin to raw !
tcsetattr(0, 0, &cnctl);
}
int scom_open_port()
{
int i, iod;
if (scom.open == OPEN)
{
close(scom.iod);
scom.open = CLOSE;
}
if ( (iod = open( scom.port, (O_RDWR | O_NOCTTY))) == -1)
{
conres(); /* Reset the console. */
fputs("term : Open Failure on device\n", stdout);
return -1;
}
scom.iod = iod;
scom.open = OPEN;
scom.update = NO_UPDATE;
}
int scom_close_port()
{
scom.open = CLOSE;
close(scom.iod);
}
int conres()
{
return(tcsetattr(0, 0, &coctl));
}
This program prints out Success.