[zeromq-dev] Delphi Wrapper Works!

Pavol Malosek malosek at fastmq.com
Tue Jul 21 14:20:24 CEST 2009

Hello Daniele,

>1. Does exist a users management in ZeroMQ? How I can limit users able connect 
>to the system?

There is not user management as you may think of. 0MQ is intended to be used in 
private trusted networks where user authentication is not an issue.
Anyway you can still bind global object to defined ports and filter network 
trafic with some kind of firewall.

>2. How works "global objects" the config file? How I can use those?

When global queue or exchange are created their names and network paths are 
stored into zmq_server (registration).
(Note that registrations are remaining in zmq_server till zmq_server restart.)
Client binding to some global object is performing a query to zmq_server to find 
object network path (protocol, IP, port...).
The problem may be that global object has to be already registered - means 
running (otherwise there is an assert in bind function).
To avoid necessity to "start" global objects first, zmq_server config file can 
be used.

Check http://zeromq.wdfiles.com/local--files/area:docs-v06/zmq_server.pdf for 
config file syntax.

>3. How I can dump server queues status? (who is connected with who)

The only one debug info is in zmq_server when compiled with defined ZMQ_TRACE 
zmq_server then prints out global object registrations and lookup requests.

>4. What is the difference between STYLE_DATA_DISTRIBUTION and 

style argument specifies the algorithm the exchange should use to distribute
messages to the bound queues. style_data_distribution means that each message is 
sent to
all the bound queues. style_load_balancing means that each message is sent to 
exactly one queue.
Messages are distributed among the queues in round-robin fashion.

>5. What is queue "SWAP"? In with cases is usefull?
When creating a queue, the size of swap can be defined. Once the queue runs out 
of its memory limit (defined by high watermark) subsequent messages are written 
to a file. When the memory usage of the queue gets below the low watermark, data 
are retrieved from the swap and placed in memory.

>If you want , I can release my Delphi code to the community.

Yes sure, but to be part of 0MQ it has to released it under MIT license.

>Thanks for your attention.

You are welcome.


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