RE: Question about SOCK_SEQPACKET

From: David Laight
Date: Fri May 05 2017 - 07:21:24 EST

From: Steven Whitehouse
> Sent: 05 May 2017 11:34
> Just before the part that you've quoted, the description for
> "The SOCK_SEQPACKET socket type is similar to the SOCK_STREAM type, and
> is also connection-oriented. The only difference between these types is
> that record boundaries are maintained using the SOCK_SEQPACKET type. A
> record can be sent using one or more output operations and received
> using one or more input operations, but a single operation never
> transfers parts of more than one record."

Right SOCK_SEQPACKET is for protocols like ISO transport.
There is no limit on the length of a 'record'.
I've written file transfer programs that put the entire file
data into a single 'record'. The receiver disconnected on
receipt of the 'end of record'.

The socket man pages could easily be wrong - they are very IP-centric.
Remember ISO transport use declined when Unix became more popular
back in the mid 1980s. Unix sockets have never really been used for
it - the address information needed just doesn't match that IP
(especially IPv4).