<![CDATA[Communication via QTcpSocket for data > 8192 bytes]]>Hey there,
I want to exchange a QJsonObject between Server and Client. My code works for not to large data, but when the data is above a size of 8192 Bytes, it doesn't work anymore, although I am sure I take care of multiple packages.
Maybe someone has an idea.
Code as follows:
@
//write
QByteArray p_ByteArray;
QDataStream p_DataSteam(&p_ByteArray, QIODevice::WriteOnly);
p_DataSteam << (int) -1;
p_ByteArray.append(QJsonDocument(i_JsonObject).toJson());
p_DataSteam.device()->seek(0);
p_DataSteam << (int) p_ByteArray.size();

int p_Sent = 0;
while(p_Sent<p_ByteArray.size())
{
p_Sent += i_Socket->write(p_ByteArray.mid(p_Sent,SENT_SIZE));
i_Socket->waitForBytesWritten(WAIT_TIME);
}

if(p_Sent==p_ByteArray.size())
return EXIT_SUCCESS;
else
{
printf("Err: writeSaveJSON failed\n");
return EXIT_FAILURE;
}
@

@
//read
QByteArray p_ByteArray;
QDataStream p_DataStream(&p_ByteArray, QIODevice::ReadOnly);
p_ByteArray = i_Socket->read(sizeof(int));

int p_ByteSize;
p_DataStream >> p_ByteSize;

while(p_ByteArray.size()<p_ByteSize) // endless loop, since no further data received
{
int p_ToRead = p_ByteSize - (int)p_ByteArray.size();
QByteArray p_ByteArray2 = i_Socket->read(p_ToRead); // this one is empty after first call
p_ByteArray.append(p_ByteArray2);
//p_ByteArray.append(i_Socket->read(p_ByteSize-p_ByteArray.size()));
}
if(p_ByteArray.size()!=p_ByteSize)
{
printf("Err: readSaveJSON failed %d %d\n",p_ByteArray.size(),p_ByteSize);
}
p_ByteArray=p_ByteArray.mid(sizeof(int),p_ByteArray.size()-sizeof(int));
return QJsonDocument::fromJson(p_ByteArray).object();
@

SENT_SIZE is set to 4096, but that should not matter, I hope.

Any ideas?

kind regards,
curator

]]>https://forum.qt.io/topic/47140/communication-via-qtcpsocket-for-data-8192-bytesRSS for NodeWed, 23 Sep 2026 18:03:26 GMTFri, 17 Oct 2014 14:20:18 GMT60<![CDATA[Reply to Communication via QTcpSocket for data > 8192 bytes on Mon, 20 Oct 2014 12:39:39 GMT]]>Hi,
The line you mention only ready the size of the array, the main read is in line 12.

However, I switched temporary to readAll and it stops after 8192 bytes again

]]>https://forum.qt.io/post/248327https://forum.qt.io/post/248327Mon, 20 Oct 2014 12:39:39 GMT<![CDATA[Reply to Communication via QTcpSocket for data > 8192 bytes on Mon, 20 Oct 2014 09:34:48 GMT]]>Hi.
From the above you are writing 4096 bytes and reading only 4 bytes.
here
" p_ByteArray = i_Socket->read(sizeof(int));"
update it by

  • p_ByteArray = i_Socket->read(4096);*

if does not work then use readAll().

]]>https://forum.qt.io/post/248310https://forum.qt.io/post/248310Mon, 20 Oct 2014 09:34:48 GMT<![CDATA[Reply to Communication via QTcpSocket for data > 8192 bytes on Mon, 20 Oct 2014 07:07:44 GMT]]>Hey, thanks for replying.

If I get your answer correctly, you say that I send the size of the commited data, where the commited data is extended by the size of the original data. that is correct, but as long as I know that and take care of that in the receiving function, that should not matter?

Any further ideas or corrections of this post?

]]>https://forum.qt.io/post/248281https://forum.qt.io/post/248281Mon, 20 Oct 2014 07:07:44 GMT<![CDATA[Reply to Communication via QTcpSocket for data > 8192 bytes on Fri, 17 Oct 2014 22:53:15 GMT]]>Hi,

@p_DataSteam << (int) p_ByteArray.size(); << wrong size@

You are giving the size of the complete array, you should only give the payload size

]]>https://forum.qt.io/post/248046https://forum.qt.io/post/248046Fri, 17 Oct 2014 22:53:15 GMT