I am surprised it is stated that TCP does not guarantee that message is
received. It does so. It guarantees packet delivery and packet order.
TCP does not guarantee packet delivery. Yes it will retransmit an
unacknowledged packet but that's quite a bit short of guaranteed delivery.
I guess they meant that with sockets, reception at TCP/IP level does
not imply
consumption of the buffer by the receiving program.
This true, but I think they meant that when an application sends data on
a socket, the fact that the system call has returned tells you _nothing_
about where the data has arrived. It might still be sitting in a buffer
on sending node. Its ethernet cable might be yanked the next milisecond
and the packet would go exactly nowhere, ever.
