Sending Large file over QTcpSocket

[SlayH]

@JonB Yeah You are right. I should have embedded the stream with an end file marker or how many packets there are. Gonna try to do it now.

[Ronel_qtmaster]

@JonB that is why i suggested upload as the first solution because it uses a boundary at the beginning
@SlayH this is an exemple for uploading an image and text

QHttpMultiPart *multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);

QHttpPart textPart;
textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name="text""));
textPart.setBody("my text");

QHttpPart imagePart;
imagePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("image/jpeg"));
imagePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name="image""));
QFile *file = new QFile("image.jpg");
file->open(QIODevice::ReadOnly);
imagePart.setBodyDevice(file);
file->setParent(multiPart); // we cannot delete the file now, so delete it with the multiPart

multiPart->append(textPart);
multiPart->append(imagePart);

QUrl url("http://my.server.tld");
QNetworkRequest request(url);

QNetworkAccessManager manager;
QNetworkReply *reply = manager.post(request, multiPart);
multiPart->setParent(reply); // delete the multiPart with the reply

[JonB]

@SlayH said in Sending Large file over QTcpSocket:

with an end file marker

How are you going to do that when sending packets which contain any pattern of binary bytes read from a file? I think you will need to precede by a byte count (or packet count or some kind of "special/empty" packet at the endif you really wish, but as I said I don't think your packet-ization achieves anything at all or what you might think it achieves).

Also, as I said earlier. I assume your ready_read() is (supposed to be) a slot for readyRead() signal? Then as long as you have a pattern like

    while (_socket->bytesAvailable())
        data << _socket->readAll();

and assume (as you do) that data will be some kind of "complete set of data or packets" then your algorithm is fatally flawed. Might work for a bit/some cases, might not. You are assuming a relationship which does not exist, such as that for each _socket->write(packet) you will receive some single read, which is not at all true. This is partly why giving up on packets and just sending a byte count followed by a stream of binary bytes would be simpler.

[JonB]

@Ronel_qtmaster
What makes you think the OP has any kind of HTTP server here? I don't see that he has indicated any such thing?

[Ronel_qtmaster]

@JonB it is just an exemple.If he has a QTcpServer listening to 127.0.01 and port 455 for exemple, he can change the url to QUrl("Http://127.0.0.1:455"), which will reach the tcpserver listening

[JonB]

@Ronel_qtmaster
And this QTcpServer will be able to service HTTP requests, so that you can send your file with QHttpMultiPart which is what you are advocating? Without any Q[Abstract]HttpServer? I must be misunderstanding something then.

[SlayH]

@JonB Yeah ready_read() is a slot for readyRead(). I did think that for each _socket->write(packet) there will be an emitted signal for readRead() but You told me it isn't the case.``` If I am supposed to send a byte count followed by a stream of binary bytes, how would it be then ???
code_text

[JonB]

@SlayH said in Sending Large file over QTcpSocket:

I did think that for each _socket->write(packet) there will be an emitted signal for readRead()

That's what I tried to say at the outset, because so many people assume it. It is not the case, at all sorts of levels in the handling.

I'm not going to write full code. In outline all you have to do is

int size = ...;
sendsocket->write(&size, sizeof(size));
sendsocket->write(fileContent, size);

at sender side.

At receiver side, read that initial size and then keep writing received bytes to file till that many bytes have been read. All reads go through onReadyRead slot, but you can only assume that will receive 1 or more bytes any time it's called. You need to receive at least sizeof(size) bytes (allow for accumulating that many bytes over multiple calls to onReadyRead() in e.g. a class member buffer), all subsequent bytes can go to output file counting up/down to that many.

You may want to think about how to send that int (do you care about byte-order for cross-platform?). You may find QDataStream's Using Read Transactions useful if you don't want to write your own stuff. (You may only want to use that for the leading int. For the "potentially large" amount of data which follows for the file content you will not want to read all of that into memory/a variable, rather only "chunks" at a time from whatever happens to have arrived there, immediately copied out to destination file.)

[SlayH]

@JonB Thanks. I'm gonna try it.

[SGaist]

Hi,

Since you are using QDataStream, you can use transactions.

[Ronel_qtmaster]

@JonB Yes exactly.The only thing is that he will have to remove the request headers from the sent packet, and put the original data in a file.

In a nutshell, when sending files with upload, the request headers are sent with the file data.You just need to separate both and keep the essential part