QTcpSocket does not send data immediately

[ChrisW67]

There's no such beast as an unbuffered TCP socket, a point made by the QTcpSocket docs:

Note: TCP sockets cannot be opened in QIODevice::Unbuffered mode.

You queue stuff to send and the TCP/IP stack looks after sending it, pipeline optimisation, acknowledgement, sequencing, and integrity. It gets there when it gets there... and you can be sure it will.