Question: I'm writing a program that uses QUdpSocket for transmitting data over the network. This is my first socket program, and I've come across an interesting problem called Endianness.

My actual question in, do I have to worry about Endianness when I'm using QNetwork as my sockets library? If I do have to worry, what do I have to do to properly avoid Endianness problems?

Answer: 
If you are transferring binary data between two machines with a different endianess you may have to worry.

The network socket will just ship the data unchanged. If the other machines assumes that the bytes it was sent are in a particular order you have to manage that.

If you are transferring data in a known format, like an image then image format generally has something in the header to show what order it was written in and the reader/writer library will handle it.
If you are inventing your own binary format - then it's upto you. You may also have to consider size, how many bytes is an int on the other machine? 

The good news, most machines are Intel and for most applications shipping smaller amounts of data in ascii format will work.
Intel CPUs use little endian. Most everything else is big endian. The default network byte order is big endian.

To test if endianness is a problem, send the value 0x12345678 and check if it makes it as the same or 0x78563412. If the value on the receiving computer is the later value, then the endianness is not the same between the two systems.

Check [this wikipedia article](http://en.wikipedia.org/wiki/Endianness) for info on endianness.