QAbstractSocket cannot receive empty (zero-length) datagrams in unix

QAbstractSocket implementation for unix platform uses system call read() instead of recv() for receiving incoming data (regardless of socket type).

But there are difference between them described in man recv(2):

If a zero-length datagram is pending, read(2) and recv() <...> provide different behavior. In this circumstance, read(2) has no effect (the datagram remains pending), while recv() consumes the pending datagram.

It means that QAbstractSocket initialized with socket descriptor of SOCK_DGRAM type cannot be used to receive datagrams properly.