From Forum Nokia Wiki

The following article shows how to show the progress of a file being downloaded using the HTTP Client.

Many times we would like to show the amount or the percentage of file that has been downloaded during the transfer. This can be achieved in the MHFRunL function.

Get the total file size of the file being downloaded

Use the case EGotResponseHeaders for this

RHTTPResponse resp = aTransaction.Response();
RHTTPHeaders headers = resp.GetHeaderCollection();
RStringPool string_pool = iSession.StringPool();
RStringF contLength = string_pool.StringF(HTTP::EContentLength, RHTTPSession::GetTable());
 
THTTPHdrVal tempHdrVal;
TInt err = headers.GetField(contLength,0,tempHdrVal);
if(err == KErrNone)
{
	iRemoteFileSize = tempHdrVal.Int();
}
else
{
	iRemoteFileSize = 0;
}

here iRemoteFileSize is the total file size of the file being downloaded. If for some reason the file size cannot be acquired set it to zero, in this case progress cannot be shown.

Show progress

Use the case EGotResponseBodyData for this

MHTTPDataSupplier* dataSupplier = aTransaction.Response().Body();
TPtrC8 ptr;
dataSupplier->GetNextDataPart(ptr);
 
TInt kb=0;
TBuf<100> str;
 
iBytes = iBytes + ptr.Length();
kb=iBytes;
if(iRemoteFileSize >0 && kb > 1024) // show percentage
{
	kb=(TInt)((kb*100)/iRemoteFileSize);
	_LIT(KFormat,"%d %% Recieved");
	str.Format(KFormat,kb);
	iDlg->SetTextL(str);
}
else
{					
	if(kb < 1024)
	{
		_LIT(KFormat,"Receiving File : %d Bytes");	//show bytes			
		str.Format(KFormat,kb);
		iDlg->SetTextL(str);
	}
	else
	{
		kb = (TInt) kb/1024;
		_LIT(KFormat,"Receiving File : %d KB");	 // show in kb					
		str.Format(KFormat,kb);
		iDlg->SetTextL(str);
	}
}

here iDlg (CAknWaitDialog) is used to show the progress of the download.