The solution to that problem is to insert the following call to the constructor of the file processing class:

QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));

Concerning the shell:
I use BusyBox (its light) which doesn't provide locale and the environment variables like LANG=en_US.UTF-8.
For compiling BusyBox configurations can or have to be given containing

CONFIG_LAST_SUPPORTED_WCHAR=0

the number is the last displayable number of the Unicode list, 0 signifies that all characters shall be displayed, it was set to 767 which includes west European characters. The excluded characters are replaced by the character defined in the same configs, in my case it is "?".

[SOLVED]

Replace

playlist->load(QUrl::fromLocalFile("C:/Users/Marco/Music/default.m3u"), "m3u");

with

QFile inputFile("C:/Users/Marco/Music/default.m3u"); if (inputFile.open(QIODevice::ReadOnly)) { QTextStream in(&inputFile); in.setCodec("UTF-8"); while (!in.atEnd()) { QString line = in.readLine().trimmed().toUtf8().constData(); playlist->addMedia(QUrl(QFileInfo(line).filePath())); } inputFile.close(); }

and

playlist->save(QUrl::fromLocalFile("C:/Users/Marco/Music/default.m3u"), "m3u");

with

QFile outputFile("C:/Users/Marco/Music/default.m3u"); outputFile.open(QIODevice::WriteOnly|QIODevice::Text); for (int i=0; i < playlist->mediaCount(); i++) { //… QTextStream out(&outputFile); out << mediafile[0].toUpper()+mediafile.mid(1) << endl; //… } outputFile.close();

@Rohith
instead of converting the unicode string to the escaped characters send it directly in binary form. When you have a QString already you can call QString::toUtf8() and send the returned QByteArray directly. On the client its enough to do QString::fromUtf8( receivedUtf8ByteArray.constData() )

It depends how you implemented the transfer.
But theoretically it should be enough to replace your unicode escaping code on the server with this approach.

@Mark81
Curious. What about:

qDebug() << (QString::fromUtf8(value) == QStringLiteral("citt\u00E0"));

Where value is the JSON value of that particular field (i.e. città).

PS.
What I'm trying to figure out is if this is an output issue, or encoding issue.

@SGaist That is true, thanks!

Windows? That explains :-)
I tested on Linux.
I don't know how to fix this on Windows.
Maybe this can help you: http://stackoverflow.com/questions/388490/unicode-characters-in-windows-command-line-how

If I'm not completely mistaken Qt 4.8 does not assume c-strings to be in UTF-8 by default,
but instead assumes they are in the systems default encoding. Have you tried with:
QString::fromUtf8("mystring");?

@SGaist Its using Serif. In the terminal there, when he run the app the follow error appears: Qt fontDatabase: cannot find font directory /home/user.../ . Is qt install correctly?
I think the app is searching for a font in the folder of Qt. But if i make the app static, this font dont need be with the app? Well if i need to copy the font files, how to link to my app?

Good idea, voted !