Problems with TCP Raw Data

[wysota]

I am not able to see the other end because it is a GPS device that transmits and receives data.

And it uses QDataStream??????????????????????????? I never heard of a GPS device using QDataStream as its communication protocol... Are you sure of that? Or have I misunderstood your "yes" answer to my question about whether the data was serialized using QDataStream?

[milot]

It uses TCP as communication protocol, for that reason I am trying to read from QTcpSocket using QDataStream!

As far as you can see on my example above, it receives data as expected and sends the data back to the device, because if I don't send data back to the device I am not able to receive any more data. For sending and receiving I data I'm using QDataStream, I pasted code above that I am able to read the header using QDataStream and write to the device using writeRawBytes() function.

[wysota]

QDataStream is not a general purpose stream for reading and writing non-textual data. It is a serialization mechanism with its own protocol. You can't use it to read data from an arbitrary binary stream. Using only readRawBytes() and writeRawBytes() with QDataStream only adds overhead without giving anything in return. If you know how many bytes to read then just read them and interpret them the way the other end of the communication expects you to.

[milot]

Thank you for the clarification.

Now I am avoiding using QDataStream, because in general serialization purposes I use QDataStream very often, and after reading that it has support for readRawData I thought it was the way to go.

Thank you again, whenever I come with a solution I will inform the others in this post as well.

[wysota]

Your problem is probably that you are going out of sync somewhere with your data. You have to remember you can't just read all data that is available in the socket and expect it to contain exactly as many bytes as you would want. Data needs to be buffered and reading needs to be deferred to a time when you are sure the buffer contains all the data you need.