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: 
Generally, you need to worry about endianness (byte-order) when you transfer integers larger than a single byte from one computer to another. In C/C++, this means that if you're sending something like a 16-bit, 32-bit or 64-bit integer, you need to first convert the integer to *network byte order*, (also known as Big-Endian). The computer on the receiving end must then convert the incoming integers to *host byte order*, which is whatever byte-order the host-machine uses natively. This is usually done using the `htons` and `ntohs` series of library functions, but with the Qt library you can also use the `qToBigEndian` and `qFromBigEndian` functions.

Note that you don't need to worry about endianness when sending ASCII or UTF-8 text, because these formats are composed of sequences of individual bytes, rather than multi-byte data types.
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.