Sending data through socket spaces, receiving with spaces

问题

I'm using C++ with QT4 for this. And when I try to send large html files(in this case, 8kb), the process of sending and receiving work well. But the file received come with spaces between each character of the html file. Here an example, the file is sent like this:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html><head><meta name="qrichtext" content="1" /><style type="text/css">
p, li { white-space: pre-wrap; }
</style></head><body style=" font-family:'MS Shell Dlg 2'; font-size:8.25pt; font-weight:400; font-style:normal;">
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">a</p></body></html>

and it's received, like this:

  ¼ < ! D O C T Y P E   H T M L   P U B L I C   " - / / W 3 C / / D T D   H T M L   4 . 0 / / E N "   " h t t p : / / w w w . w 3 . o r g / T R / R E C - h t m l 4 0 / s t r i c t . d t d " > 
 < h t m l > < h e a d > < m e t a   n a m e = " q r i c h t e x t "   c o n t e n t = " 1 "   / > < s t y l e   t y p e = " t e x t / c s s " > 
 p ,   l i   {   w h i t e - s p a c e :   p r e - w r a p ;   } 
 < / s t y l e > < / h e a d > < b o d y   s t y l e = "   f o n t - f a m i l y : ' M S   S h e l l   D l g   2 ' ;   f o n t - s i z e : 8 . 2 5 p t ;   f o n t - w e i g h t : 4 0 0 ;   f o n t - s t y l e : n o r m a l ; " > 
 < p   s t y l e = " - q t - p a r a g r a p h - t y p e : e m p t y ;   m a r g i n - t o p : 0 p x ;   m a r g i n - b o t t o m : 0 p x ;   m a r g i n - l e f t : 0 p x ;   m a r g i n - r i g h t : 0 p x ;   - q t - b l o c k - i n d e n t : 0 ;   t e x t - i n d e n t : 0 p x ; " > < / p > < / b o d y > < / h t m l >

the code i'm using for sending and receiving:

Sending code: qDebug() << "Connected. Sending file to the server"; QString text = ui->QuestHtmlText->toPlainText();

if(text.length() < 1024)
{
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out << quint16(0) << QUESTION_HTML;
    out << text;
    out.device()->seek(0);
    out << quint16(block.size() - sizeof(quint16));
    qDebug() << "Block size: " << block.size();
    socket.write(block);
    return;
}

for(int i = 0; i < text.length(); i+=1024)
{
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out << quint16(0) << QUESTION_HTML;
    if((text.length() - i) > 1024)
        out << text.mid(i, i+1024);
    else
        out << text.right(1024 - i);
    out.device()->seek(0);
    out << quint16(block.size() - sizeof(quint16));
    qDebug() << "Block size: " << block.size();
    socket.write(block);
}

Receiving code:

qDebug() << "Writing File";
QDataStream in(this);
QString temp = "Teste.html", text;
QFile myFile(".//Questions//" + temp);
myFile.open(QIODevice::WriteOnly);
QDataStream out(&myFile);
while(!in.atEnd())
{
    in >> text;
    out << text;
}

回答1:

I bet there are not spaces between characters (but 0s) & you get the extra chars due to your use of quint16.

回答2:

@Eugen i suspect the quint16 is either not written at all or is at the end of the file. Read below.

@Patrick don't repost only because you feel like not being served fast enough. Stackowerflow is not a hotline.

The stuff you are getting back in the file is not your original text, but QString serialization form, which is unsuprisingly UTF-16. If you want your text back, read the input QDataStream back to QString and save that into file.

While prefixing your data with a length is generally a good idea, it is absolutely redundant with QString >> QDataStream. Read up something here or here. Moreover you have developed a mind boggingly obfuscated way which i suspect is doing nothing. QByteArray is not implementing QIODevice (indeed, why it should) so your out.device()->seek() is a base virtual implementation, empty and just returning true. I won't be surprised if your length "header" is found at the end of your serialization dump file.

Edit: i think that your html transport might start working correctly only by leaving out the confused quint operation completely and use out QTextStream instead of QByteStream.

回答3:

I solved the problem writing it to a file and getting this file to a QByteArray, and sending the QbyteArray entirely to the socket.

来源：https://stackoverflow.com/questions/10890161/sending-data-through-socket-spaces-receiving-with-spaces

标签

html

c++

sockets

large-data