Data protocol

The data protocol transmits messages from publishers to subscribers via a proxy server in a broadcasting fashion.

Transport layer

The transport layer ensures that a message arrives at its destination.

Socket configuration

A proxy server is the transmitting station, it shall offer an XSUBSCRIBER and an XPUBLISHER socket. The two sockets shall be connected, e.g. via the zmq.proxy_server method. Each of both sockets shall be bound to its own address.

A Publisher is a Component, which sends data messages via the data protocol. It shall have a PUBLISHER socket connecting to the proxy server’s XSUBSCRIBER socket.

A Subscriber is a Component, which wants to reveice data messages via the data protocol. It shall have a SUBSCRIBER socket connecting to the proxy server’s XPUBLISHER socket. It should subscribe to the Topics it wants to receive.

Note

Subscribing to a topic in zmq means to subscribe to all topics which start with the given topic name!

Recommended configuration

It is recommended to have a single program with two proxy servers. The first one transfers any data and binds its XSUBSCRIBER to port number 11100 and binds its XPUBLISHER to 11099. The second one transfers log entries and binds to 11098 and 11097, respectively.

Message format

A Data Protocol Message consists in three or more frames (#62):

Topic
Header
One or more data frames, the first one is the Content

Topic

The topic is the full name of the sending Component. (#60)

Content

Log message content

For log messages, the content is a JSON encoded list of:

record.asctime: Timestamp formatted as '%Y-%m-%d %H:%M:%S'
record.levelname: Logger level name
record.name: Logger name
record.text (including traceback)