Subclassing socket

[Bryan Olson]

groups.20.thebriguy at spamgourmet.com wrote:
> To your question of why you'd ever [recv(0)].
> 
> This is very common in any network programming.  If you send a packet
> of data that has a header and payload, and the header contains the
> length (N) of the payload, then at some point you have to receive N
> bytes.  If N is zero, then you receive 0 bytes.  Of course, you CAN
> test for N == 0, that's obvious - but why would you if the underlying
> layers worked correctly?  Its just extra code to handle an special case.

We need "extra code" around recv to ensure we get exactly
N bytes; 'recv(N)' can return less. The most straightforward
code I know to read exactly N bytes never passes zero to
recv (untested):


def recvall(sock, size):
     """ Read and return exactly 'size' bytes from socket 'sock'.
         Kind of the other side of sock.sendall.
     """
     parts = []
     while size > 0:
         data = sock.recv(size)
         if not data:
              raise SomeException("Socket closed early.")
         size -= len(data)
         parts.append(data)
     return ''.join(parts)


-- 
--Bryan