With the introduction of subscription forwarding, the first message sent
on a PUB socket using a unidirectional transport (e.g. PGM) is always
lost due to the "subscribe to all" being done asynchronously.

This patch fixes the problem and also refactors the code to have a single
point where the "subscribe to all" is performed.
Signed-off-by: Martin Lucina <martin@lucina.net>

Opening any PGM socket gives this assertion. The problem is in
pgm_sender_t::plug() which is incorrectly testing the return value from
session::write().
Signed-off-by: Martin Lucina <martin@lucina.net>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

This is a preliminary patch allowing for socket-type-specific
functionality in the I/O thread. For example, message format
can be checked asynchronously and misbehaved connections dropped
straight away.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

On win64 the size of file descriptor is not the same as size of int.
The bug in PGM transport caused a runtime error because of this.
The problem is fixed now.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

PGM when using in XPUB socket has to subscribe for all the messages
as it has no idea what the subscribers are interesred in.
This generic subscribe message was malformed. Fixed.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Removal of ZMQ_IDENTITY resulted in various session classes doing
almost the same thing. This patch merges the classes into a single
class.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

As PGM is not capable of passing subscriptions upstream,
subscriptions are ignored at sub side and engine subscribes
for all messages on pub side.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Toralf Wittner <toralf.wittner@gmail.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Steven McCoy <steven.mccoy@miru.hk>

This commit introduces the necessary changes necessary
for implementing flow control. None of the socket types
implements the flow control yet. The code will crash when
the flow control is enabled and the thw lwm is reached.

The following commits will add flow-control support for
individual socket types.

zmq_encoder/decoder are able to add/trim prefixes from messages; fair queueing and load balancing algorithms factorised into separate classes