How to transfer file through serial communication

**wysota** · 28th May 2007, 13:24

Is it me or are you trying to send a QString object through the line? I'm surprised it even compiles... Provided that your write() calls really mean ::write() then the second argument should be a pointer to a const char* buffer. Could you paste the real and current code you're using? Because I don't think there is a strlen() variant that takes a QString as well...

**shamik** · 28th May 2007, 13:38

the code which i've posted b4 is the one which i m using currently.

if u think sending a QString object cud b erroneous then plz suggest wat 2 use instead. i very well know that the second argument requires const char * but the problem is i dont know how to define/declare it and secondly the getch() function returns an integer, again i donno how to convert that integer into const char * . so i just tried to use QString

i hope now this is not a difficult question 4 u
please help...

**marcel** · 28th May 2007, 13:45

Use QString::toAscii().constData( means const char *).

Regards

**high_flyer** · 29th May 2007, 09:11

And PLEASE - DON'T use sms lingo here! it is so anoying to read it like that, and there is NO reason for it, unless you are posting through WAP on your mobile.

**shamik** · 29th May 2007, 09:18

the function as said above doesnt work
it says theres no such function as QString::toAscii() etc..
anyways i have done some changes to the code. the entire code is as below :

Qt Code:

Switch view

void Form1::send_clicked()
{
    int size;
    int i,j,k;
    QString send;
    QFile file("/sfiles/mxdrv.tgz");
    if(!file.open( IO_ReadOnly ))
    {
    	QMessageBox::information(0,"Error","Error opening file");
    }
    else
    {
    	cout<<"File opened successfully"<<endl;
    }
    cout<<"file opened...."<<endl;
    unsigned char fname[]="mxdrv.tgz";
  struct termios t;
  char *device = "/dev/ttyS0"; 
  int sPort, rbyte, status, sPortdest,length;
  long count=0; 
  unsigned char send1[32];    
 
  t.c_cc[VMIN] = 1;
  t.c_cc[VTIME]=0;
  t.c_cc[VEOF]='\n';
 
  t.c_iflag |= (ISIG);
  t.c_iflag &= ~BRKINT;	
  t.c_cflag = B9600 | CS8 | CREAD | CLOCAL | HUPCL;
 
  sPort = open(device,O_RDWR|O_NOCTTY|O_NDELAY);
 
  	if(sPort != -1)
	{
		cout<<"open successfully\n";
 
		status = ioctl(sPort,TCSETS,&t);
		cout<<"Entering status"<<status<<endl;
		if(status==0)
	      	{	     
			//for(count=0;count<20;count++)
			cout<<"sending name"<<endl;
			rbyte=write(sPort,fname,strlen((char *)fname));
			cout<<rbyte<<endl;			
			QMessageBox::information(0,"sent","Name sent");
			//usleep(3000);
			cout<<"name sent"<<endl;
			cout<<"now sending file"<<endl;
			usleep(3000);
			while(!file.atEnd())
 
			{   
				//cout<<"Enter :";
				//cin>>send1;
                               //strcat((char *)send1,"{MSS TYPE-D DAMA}");
//	write(sPort,"{012345678}",11);	
				cout<<"getting byte from file"<<endl;
				i=file.getch();	
				GenerateByte(i,send);	
				//usleep(3000);
				rbyte=TEMP_FAILURE_RETRY( write(sPort,send,qstrlen(send)));
				cout<<rbyte<<"sent"<<endl;
				//cout<<"w b:"<<rbyte<<"\t Time:"<<count<<"\t string:"<<send1<<"\n";
				//usleep(1000);
 
			}	
 
		  }
		  close(sPort);		
	}
	else
	{
		cout<<"Device could not be opened";
	}
	file.close();
}
void Form1::GenerateByte(int i, QString &ssend)
{
	ssend.sprintf("%d",i);
}

void Form1::send_clicked()
{
    int size;
    int i,j,k;
    QString send;
    QFile file("/sfiles/mxdrv.tgz");
    if(!file.open( IO_ReadOnly ))
    {
    	QMessageBox::information(0,"Error","Error opening file");
    }
    else
    {
    	cout<<"File opened successfully"<<endl;
    }
    cout<<"file opened...."<<endl;
    unsigned char fname[]="mxdrv.tgz";
  struct termios t;
  char *device = "/dev/ttyS0"; 
  int sPort, rbyte, status, sPortdest,length;
  long count=0; 
  unsigned char send1[32];    

  t.c_cc[VMIN] = 1;
  t.c_cc[VTIME]=0;
  t.c_cc[VEOF]='\n';
  
  t.c_iflag |= (ISIG);
  t.c_iflag &= ~BRKINT;	
  t.c_cflag = B9600 | CS8 | CREAD | CLOCAL | HUPCL;
  
  sPort = open(device,O_RDWR|O_NOCTTY|O_NDELAY);
  
  	if(sPort != -1)
	{
		cout<<"open successfully\n";
		
		status = ioctl(sPort,TCSETS,&t);
		cout<<"Entering status"<<status<<endl;
		if(status==0)
	      	{	     
			//for(count=0;count<20;count++)
			cout<<"sending name"<<endl;
			rbyte=write(sPort,fname,strlen((char *)fname));
			cout<<rbyte<<endl;			
			QMessageBox::information(0,"sent","Name sent");
			//usleep(3000);
			cout<<"name sent"<<endl;
			cout<<"now sending file"<<endl;
			usleep(3000);
			while(!file.atEnd())
						
			{   
				//cout<<"Enter :";
				//cin>>send1;
                               //strcat((char *)send1,"{MSS TYPE-D DAMA}");
//	write(sPort,"{012345678}",11);	
				cout<<"getting byte from file"<<endl;
				i=file.getch();	
				GenerateByte(i,send);	
				//usleep(3000);
				rbyte=TEMP_FAILURE_RETRY( write(sPort,send,qstrlen(send)));
				cout<<rbyte<<"sent"<<endl;
				//cout<<"w b:"<<rbyte<<"\t Time:"<<count<<"\t string:"<<send1<<"\n";
				//usleep(1000);
		
			}	

		  }
		  close(sPort);		
	}
	else
	{
		cout<<"Device could not be opened";
	}
	file.close();
}
void Form1::GenerateByte(int i, QString &ssend)
{
	ssend.sprintf("%d",i);
}

To copy to clipboard, switch view to plain text mode

and about using the QString object in write() function, i have checked it with the previous code of my project, and it is working fine. The only thing is instead of strlen() i have to use qstrlen().
the code which i have pasted above doesnt give any error while compiling but while transferring file what happens exactly is that the write() function sometimes returns some positive integer and sometimes returnds -1. but most of the time it returns -1.
then after some time the following comes on the terminal :
*** glibc detected *** ./filetransfer: munmap_chunk(): invalid pointer: 0xbfab4940 ***
======= Backtrace: =========
/lib/libc.so.6(cfree+0x1bb)[0xbb267b]
/usr/lib/libstdc++.so.6(_ZdlPv+0x21)[0x6874871]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QWidget5closeEb+0x1f6)[0x5198e6]
./filetransfer[0x8050af0]
./filetransfer[0x804fb7f]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QObject15activate_signalEP15QConnectio nListP8QUObject+0x16a)[0x4dbe2a]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QObject15activate_signalEi+0xbd)[0x4dc95d]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QButton7clickedEv+0x2c)[0x86f8ac]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QButton15keyReleaseEventEP9QKeyEvent+0 x5a)[0x57fd5a]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN7QWidget5eventEP6QEvent+0x325)[0x519235]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN12QApplication14internalNotifyEP7QObjec tP6QEvent+0x9b)[0x4730fb]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN12QApplication6notifyEP7QObjectP6QEvent +0x54d)[0x474a1d]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN9QETWidget17translateKeyEventEPK7_XEven tb+0x36a)[0x408b0a]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN12QApplication15x11ProcessEventEP7_XEve nt+0x635)[0x409a75]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN10QEventLoop13processEventsEj+0x4eb)[0x41b6ab]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN10QEventLoop9enterLoopEv+0x42)[0x48c672]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN10QEventLoop4execEv+0x26)[0x48c536]
/usr/lib/qt-3.3/lib/libqt-mt.so.3(_ZN12QApplication4execEv+0x1f)[0x472c0f]
./filetransfer(_ZN7QWidget6createEmbb+0xe37)[0x804f04f]
/lib/libc.so.6(__libc_start_main+0xdc)[0xb5ef2c]
./filetransfer(_ZN11KMainWindow10setCaptionERK7QStri ngb+0x49)[0x804e391]
======= Memory map: ========
00101000-00117000 r-xp 00000000 03:07 483707 /usr/lib/libart_lgpl_2.so.2.3.17
00117000-00118000 rwxp 00016000 03:07 483707 /usr/lib/libart_lgpl_2.so.2.3.17
00118000-0012d000 r-xp 00000000 03:07 686877 /usr/lib/qt-3.3/plugins/styles/bluecurve.so
0012d000-0012e000 rwxp 00015000 03:07 686877 /usr/lib/qt-3.3/plugins/styles/bluecurve.so
00132000-00163000 r-xp 00000000 03:07 483702 /usr/lib/liblcms.so.1.0.15
00163000-00164000 rwxp 00030000 03:07 483702 /usr/lib/liblcms.so.1.0.15
00164000-00167000 rwxp 00164000 00:00 0
00167000-00170000 r-xp 00000000 03:07 487954 /lib/libnss_files-2.5.so
00170000-00171000 r-xp 00008000 03:07 487954 /lib/libnss_files-2.5.so
00171000-00172000 rwxp 00009000 03:07 487954 /lib/libnss_files-2.5.so
00193000-001a5000 r-xp 00000000 03:07 483704 /usr/lib/libXft.so.2.1.2
001a5000-001a6000 rwxp 00012000 03:07 483704 /usr/lib/libXft.so.2.1.2
001a8000-00210000 r-xp 00000000 03:07 483703 /usr/lib/libmng.so.1.0.0
00210000-00213000 rwxp 00067000 03:07 483703 /usr/lib/libmng.so.1.0.0
00215000-00224000 r-xp 00000000 03:07 1329158 /lib/libresolv-2.5.so
00224000-00225000 r-xp 0000e000 03:07 1329158 /lib/libresolv-2.5.so
00225000-00226000 rwxp 0000f000 03:07 1329158 /lib/libresolv-2.5.so
00226000-00228000 rwxp 00226000 00:00 0
0022a000-00a5b000 r-xp 00000000 03:07 196091 /usr/lib/qt-3.3/lib/libqt-mt.so.3.3.6
00a5b000-00a9c000 rwxp 00830000 03:07 196091 /usr/lib/qt-3.3/lib/libqt-mt.so.3.3.6
00a9c000-00aa0000 rwxp 00a9c000 00:00 0
00ab3000-00ac2000 r-xp 00000000 03:07 483684 /usr/lib/libXext.so.6.4.0
00ac2000-00ac3000 rwxp 0000e000 03:07 483684 /usr/lib/libXext.so.6.4.0
00ac3000-00ac4000 r-xp 00ac3000 00:00 0 [vdso]
00ac5000-00ae4000 r-xp 00000000 03:07 1329151 /lib/libexpat.so.0.5.0
00ae4000-00ae6000 rwxp 0001e000 03:07 1329151 /lib/libexpat.so.0.5.0
00ae8000-00b0f000 r-xp 00000000 03:07 483675 /usr/lib/libfontconfig.so.1.1.0
00b0f000-00b17000 rwxp 00027000 03:07 483675 /usr/lib/libfontconfig.so.1.1.0
00b19000-00b21000 r-xp 00000000 03:07 483680 /usr/lib/libXrender.so.1.3.0
00b21000-00b22000 rwxp 00007000 03:07 483680 /usr/lib/libXrender.so.1.3.0
00b24000-00b28000 r-xp 00000000 03:07 483688 /usr/lib/libXfixes.so.3.1.0
00b28000-00b29000 rwxp 00003000 03:07 483688 /usr/lib/libXfixes.so.3.1.0
00b2c000-00b45000 r-xp 00000000 03:07 1329142 /lib/ld-2.5.so
00b45000-00b46000 r-xp 00018000 03:07 1329142 /lib/ld-2.5.so
00b46000-00b47000 rwxp 00019000 03:07 1329142 /lib/ld-2.5.so
00b49000-00c80000 r-xp 00000000 03:07 1329143 /lib/libc-2.5.so
00c80000-00c82000 r-xp 00137000 03:07 1329143 /lib/libc-2.5.so
00c82000-00c83000 rwxp 00139000 03:07 1329143 /lib/libc-2.5.so
00c83000-00c86000 rwxp 00c83000 00:00 0
00c88000-00cad000 r-xp 00000000 03:07 1329150 /lib/libm-2.5.so
00cad000-00cae000 r-xp 00024000 03:07 1329150 /lib/libm-2.5.so
00cae000-00caf000 rwxp 00025000 03:07 1329150 /lib/libm-2.5.so
00cb1000-00cb3000 r-xp 00000000 03:07 1329144 /lib/libdl-2.5.so
00cb3000-00cb4000 r-xp 00001000 03:07 1329144 /lib/libdl-2.5.so
00cb4000-00cb5000 rwxp 00002000 03:07 1329144 /lib/libdl-2.5.so
00cb7000-00cca000 r-xp 00000000 03:07 1329145 /lib/libpthread-2.5.so
00cca000-00ccb000 r-xp 00012000 03:07 1329145 /lib/libpthread-2.5.so
00ccb000-00ccc000 rwxp 00013000 03:07 1329145 /lib/libpthread-2.5.so
00ccc000-00cce000 rwxp 00ccc000 00:00 0
00cd0000-00ce2000 r-xp 00000000 03:07 483673 /usr/lib/libz.so.1.2.3
00ce2000-00ce3000 rwxp 00011000 03:07 483673 /usr/lib/libz.so.1.2.3
00ce5000-00cea000 r-xp 00000000 03:07 483678 /usr/lib/libXdmcp.so.6.0.0
00cea000-00ceb000 rwxp 00004000 03:07 483678 /usr/lib/libXdmcp.so.6.0.0
00ced000-00cef000 r-Aborted

i dont know wat does this mean.

can any1 please find watz going wrong

**marcel** · 29th May 2007, 09:24

When I said QString::toAscii().constData() I meant the method name and location.
But now I see you're using Qt3. Sorry about that

.
In Qt3 you must use send.ascii(). This will give you a const char*.
And you must use this, because the code is still not correct.

For length, you can use send.length() or send.size(). I don't know which one is available in Qt3.

Regards

**shamik** · 29th May 2007, 10:00

i've used send.ascii() instead of send

the qstrlen() function perfectly gives the length of the string so i dont think the problem is there.

still the output is the same.
the write() function which returns -1 only when there is an error while sending, and some other digit when data is sent corrently, most of the time gives -1 and only few times somewhere in between gives some other digits.
later after some more time, the above mentioned error comes

i donno wat is wrong over here. i think now its becoming difficult to find out.

**high_flyer** · 29th May 2007, 10:03

For length, you can use send.length() or send.size(). I don't know which one is available in Qt3.

The reason is, that qstrlen() returns the length of the given string, but QString is not a string, its a class that manages a string, so QString is an object containing a string.
send.length() will return the length of the string it self which is contained by the QString object.

you posted your last post while I was writing mine so:

the qstrlen() function perfectly gives the length of the string so i dont think the problem is there.

I can't explain this, it should not be so, because of the explanation above.
You are giving a QString object to qstrlen() and it awaits a const char*.
As wysota said, this should not even compile.

**marcel** · 29th May 2007, 10:17

qstrlen works because QString has operator const char * overloaded in Qt3.
But it is recommended not to be used.

**marcel** · 29th May 2007, 10:22

The only thing is instead of strlen() i have to use qstrlen().
the code which i have pasted above doesnt give any error while compiling but while transferring file what happens exactly is that the write() function sometimes returns some positive integer and sometimes returnds -1. but most of the time it returns -1.

See what is the value of errno after write returns -1.
Something like this( from MSDN ):

Qt Code:

Switch view

if (( bytesWritten = _write( fileHandle, buffer, sizeof( buffer ))) == -1 )
   {
      switch(errno)
      {
         case EBADF:
            perror("Bad file descriptor!");
            break;
         case ENOSPC:
            perror("No space left on device!");
            break;
         case EINVAL:
            perror("Invalid parameter: buffer was NULL!");
            break;
         default:
            // An unrelated error occured 
            perror("Unexpected error!");
      }
   }

if (( bytesWritten = _write( fileHandle, buffer, sizeof( buffer ))) == -1 )
   {
      switch(errno)
      {
         case EBADF:
            perror("Bad file descriptor!");
            break;
         case ENOSPC:
            perror("No space left on device!");
            break;
         case EINVAL:
            perror("Invalid parameter: buffer was NULL!");
            break;
         default:
            // An unrelated error occured 
            perror("Unexpected error!");
      }
   }

To copy to clipboard, switch view to plain text mode

Regards