From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-30T18:09:22+09:00
Subject: Re: Problem with socket.recv()

Robert Klemme wrote:
> 2007/10/30, Francis Cianfrocca <garbagecat10@gmail.com>:
>>
>> If the server closes the connection after sending the data, you can simply
>> use socket#read. If you need to wait for the data and then process them as
>> they comes in, use #select in a loop until all the data have been received.
> 
> There is another option - even if the server does not close after
> sending: use #read with a given size limit. #read will block and
> return as soon data is available.  

That's not what I'm seeing.  What I see is: read() blocks until it 
either receives the limit number of bytes or eof is encountered(when the 
server closes the socket).  In other words, read() does not return as 
soon as data is available if the amount of bytes read is less than the 
limit number of bytes.  On the other hand, recv() returns whatever it 
reads immediately.  Here is the code:

#server:
--------------
require 'socket'

port = 3030
server = TCPServer.new('', port)

while(conn = server.accept) #serves forever
  conn.print 'h'
  sleep(5)

  conn.print 'ello world'
  conn.close
end
--------------


#client using recv():
--------------------
require 'socket'

port = 3030
socket = TCPSocket.new('localhost', port)

all_data = []

while true
  partial_data = socket.recv(1012)
  puts partial_data

  if partial_data.length == 0
    break
  end

  all_data << partial_data
end
socket.close

puts all_data.join()

--output:--
h
ello world
                  #blank string returned when server closed socket
hello world
------------------------



#client using read():
-----------------
require 'socket'

port = 3030
socket = TCPSocket.new('localhost', port)

all_data = []

while partial_data = socket.read(1012)
  puts partial_data
  all_data << partial_data
end
socket.close

puts all_data.join()

--output: --
hello world
hello world
----------------


So the way I see it:

1) If the amount of data sent by the server is less than the size limit 
specified in read(), read() will block until the server closes the 
socket.  Therefore, the server must close the socket.

2) If the amount of data sent by the server is more than the size limit 
specified in read(), and you just write:

all_data = read(1012)
puts data

then you aren't reading all the data. You just get the first 1012 bytes.





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