What Is The Difference Between Using Zmq Pub With .connect() Or .bind() Methods?

In Python ZMQ publisher/subscriber sample template, the publisher uses .bind() method and the subscriber uses .connect() method, that connected to the bind IP address. But we can r

Solution 1:

There is no difference here (single publisher and subscriber), but in other scenarios (multi publishers or subscribers), there is a difference depending on your policy:

1. i.e. suppose that there are two clients (Machine1, Machine2) and a Server. Each client must publish data using ZMQ, and the Server must subscribe that data from Machine1 and Machine2:

• Machine1 --> has a publisher (with .connect(Server IP) )

• Machine2 --> has a publisher (with .connect(Server IP) )

• Server --> has a subscriber (with .bind(Server IP/Self IP))

As you can see in the mentioned scenario we used the second case in the question.

2. Whereas, if we have two subscribers and a publisher, we must place the .bind() method in the publisher and place .connect() method in the subscribers (first case in the question).

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Solution 2:

Operational-level difference, there is none.

Setup perspective difference - .bind() method need not know the actual addresses ( using wildcard-expansio tricks et al ), .connect() method has to know a target address to which it will start trying to .connect()-to.

Transport-class / Scalable Formal Communication Pattern Archetype - there are cases, when some order of instantiation / becoming RTO is mandatory for proper archetype service, so, yes, there are differences, when one, .bind() has to become RTO earlier, before any remote .connect() may have a chance to succeed.

Add-on specific features available for configuring the .bind() side - are the last principal set of differences, where some more recent ZeroMQ API versions 3.2+ started to add some new access-control and similar defensive options for the .bind()-side node, so as to help manage plethora of risks once going into public internet exposed modus operandi.