ZMQ Notes

ZMQ Important points

ZMQ is widely used as a reliable & easy-to-use replacement of sockets

Sync & A-Sync style sockets

In ZMQ, the sockets can be classified into two different categories:

1. Sync: like REQ/REP
2. Async: DEALER/ROUTER

Envelope

The concept of envelope is used to identify the source of each message.
For REQ socket,

1. Send the message: REQ will prepend a empty frame to the real message.
2. Receive the message: strips every frame including empty frame.

For REP socket:

1. Receive the message: Will strip frames including empty frame, then return the rest of the message to application.
2. Send the message: Prepend the message with saved envelope.

For ROUTER socket:

1. Receive the message: prepend identify frame automatically
2. Send the message: Remove the identity frame and check existence of the identity.

For DEALER socket: Do nothing, will send whatever you want in the message.

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