Writing SSE backends with Python

And here we go again with the snake...

As I mentioned in the last post, I wrote this server script for SSE in Python.

Well, I thought it would be more worthwhile to turn it into a framework kind of thing, on which you can easily build your SSE backends.


Warning: the code and stuff are in Python and I'm not going to go into details about the language here. I'll just describe the functions and classes in the framework.


The basic implementation is built on the Twisted networking framework for Python. If you want to know more about Twisted, you can find their docs from their page.


My framework consists of three classes: the SSEClient, SSEServer and Service classes.

The SSEServer class is the "main" processor. It handles reading the console for input, pinging users and sending requests to the correct Services.


The Service class is what the programmer will be mainly using.


The SSEClient is used as the client for the services. It contains the SSE request and methods to write data to the stream and such.


You can download the framework from here.

An example Service made with the framework can be downloaded from here.

The example service can be run with Python with python sseexample.py. It starts the server in port 3080.


Descriptions of the classes

SSEServer:

example = SSEServer(services,True,True)

the SSEServer takes three parameters:
a dict of the services
True/False if you want it to ping users automatically
True/False if you want it to read console input

the format for the service dict:
{'/service/path': ServiceClass(), '/second/service': SecondClass()}

For example, if you set the path to '/', the service is accessible with http://yourserver:port/ and if you set it to '/example', it's accessible with http://yourserver:port/example.




Service:

example = Service('Service name')

Service takes one parameter: the name of the service. The service itself does nothing, so you will have to make your own class which inherits from it.

Service functions:

parse(request) - this is called when a client wants to access the service. Override in your own class

findClient(request) - can be used to see if the user has already opened an SSE session. Returns the SSEClient if found, otherwise None.

startSession(client) - used to start a new SSE session. Pass an SSEClient as the parameter. After the session is created, it sends the clients session-id. Format:
Event: session-id
data:

broadcast(type,message) - sends a message to all clients. type is the event type and message is the data for the event

ping() - sends a ping to every user who hasn't received a message in the last 60 seconds. Used automatically by the SSEServer pinger.

drop(client) - removes a client from the list. Parameter is an SSEClient


SSEClient

example = SSEClient(service,request)

Parameters for the SSEClient are the "owner" service and the client's request.

You can override the SSEClient so you can add more variables to it, like the users name in a chat or something like that.

functions:

stop(reason) - automatically called when the users connection is closed. Calls the parent services drop method.

sendMsg(type,data) - send a message to the client. type is the event type and data the event data. The data can also be a list and it will be handled properly.




There we go. Feel free to ask if you have anything on your mind.