18. Messaging

18.1. Intro

Messaging is used to transfer JSON Object-Data between Network Clients including notification messages.

To enable local messaging functionality a docker container using https://github.com/clauspruefer/micro-msg-server has been set up.

Note

Docker networking has limitations, so running the messaging server on port 8080 is the only option to run x0-app and x0-msg-server in parallel.

18.2. Start Server

Start the messaging server with the following commands.

    # start messaging server
    cd ./docker
./x0-start-msg-server.sh

18.3. Internal

Internally x0-system uses long polling mechanism which still runs stable and performant on HTTP/1.1. Polling timeout is set to 10 seconds.

This method is planned to be replaced by WebSockets in the near future.

Warning

Running the micro-msg-server is not intended for production use. Some system similar to rabbit-mq should be considered when processing heavy messaging loads.

Warning

Also the messaging server code differs (patched) from the original and will only work with example code.

18.4. Example

The following example transfers form metadata from user session A over the network to user session B.

http://x0-app.x0.localnet/python/Index.py?appid=example10

To test message exchange, open the given URL in multiple (two) browser tabs and reload until two different user ids in the User ID form (user ids are random generated) will be displayed.

Now select the correct destination User Dst SessionID. Clicking the Send Data button will exchange the data and display the form data entered in the source users browser as soon as possible.

Warning

The example code does not emphasize security. It is not advisable to exchange user-sessions between network clients. Normally this is the backends job after a successful user authentication (user-id / session-id mapping).

Warning

Also to simplify things mmessage deletion occurs immediately after processing on the messaging server side. This workflow is not acceptable in real-world scenarios, the deletion has to be re-triggered after receipt on client-side.