serialfd = open( serialPortName.c_str(), O_RDWR | O_NOCTTY | O_NDELAY);

if (serialfd == -1) 
{ 
    /* 
     * Could not open the port. 
     */ 
    TRACE << "Unable to open port: " << serialPortName << endl; 
} 
else 
{ 
    TRACE << "Connected to serial port: " << serialPortName << endl; 
    fcntl(serialfd, F_SETFL, 0); 
}

    struct termios options; 
 
    /* 
     * Get the current options for the port... 
     */ 
    tcgetattr(serialfd, &options); 
 
    /* 
     * Set the baud rates to 9600... 
     */ 
    cfsetispeed(&options, B38400); 
    cfsetospeed(&options, B38400); 
 
    /* 
     * 8N1 
     * Data bits - 8 
     * Parity    - None 
     * Stop bits - 1 
     */ 
    options.c_cflag &= ~PARENB; 
    options.c_cflag &= ~CSTOPB; 
    options.c_cflag &= ~CSIZE; 
    options.c_cflag |= CS8; 
 
    /* 
     * Enable hardware flow control 
     */ 
    options.c_cflag |= CRTSCTS; 
 
    /* 
     *  Enable the receiver and set local mode... 
     */ 
    options.c_cflag |= (CLOCAL | CREAD); 
 
    // Flush the earlier data 
    tcflush(serialfd, TCIFLUSH); 
 
    /* 
     *  Set the new options for the port... 
     */ 
    tcsetattr(serialfd, TCSANOW, &options);

  const int MAXDATASIZE = 512; 
  std::vector<char> m_vRequestBuf;   
  char buffer[MAXDATASIZE]; 
  int totalBytes = 0; 
 
  fcntl(serialfd, F_SETFL, FNDELAY); 
  while(1) { 
             bytesRead = read(serialfd, &buffer, MAXDATASIZE); 
        if(bytesRead == -1) 
        { 
           //Sleep for some time and read again  
                  usleep(900000); 
        } 
        else 
        { 
            totalBytes += bytesRead;         
                  //Add data read to vector 
                  for(int i =0; i < bytesRead; i++) 
            { 
            m_vRequestBuf.push_back(buffer[i]); 
            } 
 
                  int newBytesRead = 0; 
 
                  //Now keep trying to read more data 
            while(newBytesRead != -1) 
            { 
            //clear contents of buffer 
            memset((void*)&buffer, 0, sizeof(char) * MAXDATASIZE);   
            newBytesRead = read(serialfd, &buffer, MAXDATASIZE); 
            totalBytes += newBytesRead; 
 
                        for(int j = 0; j < newBytesRead; j++) 
            { 
                m_vRequestBuf.push_back(buffer[j]); 
            } 
             }//inner while              
           break; 
        } //while