[REBOL] receiving data of unknown sizes through a port

[max]

I want to create a server that receives files (or any data) of unknown sizes
through a port.  How do I know when the EOF is reached or if the other end
has closed the port?

*** server side ***

port: open/binary tcp://:2000
buffer-size: 1024
buffer: make string! buffer-size
forever [
  io-port: first port
  wait io-port
  while [ ??? not EOF or port closed ??? ] [
      read-io io-port buffer buffer-size
;*** more code goes here
      clear buffer
  ]
  clear buffer
  close io-port
]


*** client side ***

host-port: open/binary tcp://127.0.0.1:2000
send-data: read/binary %anyfile.tst
insert host-port send-data
close host-port



Thanks for any help,
Max