ws4py comes with a few server implementations built around the main
ws4py provides an extension to CherryPy 3 to enable WebSocket from the framework layer. It is based on the CherryPy plugin and tool mechanisms.
WebSocket tool plays at the request level on every request received by the server. Its goal is to perform the WebSocket handshake and, if it succeeds, to create the
WebSocket instance (well a subclass you will be implementing) and push it to the plugin.
WebSocket plugin works at the CherryPy system level and has a single instance throughout. Its goal is to track websocket instances created by the tool and free their resources when connections are closed.
Here is a simple example of an echo server:
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Note how we specify the class which should be instanciated by the server on each connection. The great aspect of the tool mechanism is that you can specify a different class on a per-path basis.
gevent is a coroutine, called greenlets, implementation for very concurrent applications. ws4py offers a server implementation for this library on top of the WSGI protocol. Using it is as simple as:
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from gevent import monkey; monkey.patch_all() from ws4py.websocket import EchoWebSocket from ws4py.server.geventserver import WSGIServer from ws4py.server.wsgiutils import WebSocketWSGIApplication server = WSGIServer(('localhost', 9000), WebSocketWSGIApplication(handler_cls=EchoWebSocket)) server.serve_forever()
First we patch all the standard modules so that the stdlib runs well with as gevent. Then we simply create a WSGI server and specify the class which will be instanciated internally each time a connection is successful.
wsgiref is a built-in WSGI package that provides various classes and helpers to develop against WSGI. Mostly it provides a basic WSGI server that can be usedfor testing or simple demos. ws4py provides support for websocket on wsgiref for testing purpose as well. It’s not meant to be used in production, since it can only initiate web socket connections one at a time, as a result of being single threaded. However, once accepted, ws4py takes over, which is multithreaded by default.
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from wsgiref.simple_server import make_server from ws4py.websocket import EchoWebSocket from ws4py.server.wsgirefserver import WSGIServer, WebSocketWSGIRequestHandler from ws4py.server.wsgiutils import WebSocketWSGIApplication server = make_server('', 9000, server_class=WSGIServer, handler_class=WebSocketWSGIRequestHandler, app=WebSocketWSGIApplication(handler_cls=EchoWebSocket)) server.initialize_websockets_manager() server.serve_forever()
asyncio is the implementation of PEP 3156, the new asynchronous framework for concurrent
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from ws4py.async_websocket import EchoWebSocket loop = asyncio.get_event_loop() def start_server(): proto_factory = lambda: WebSocketProtocol(EchoWebSocket) return loop.create_server(proto_factory, '', 9007) s = loop.run_until_complete(start_server()) print('serving on', s.sockets.getsockname()) loop.run_forever()
The provided HTTP server used for the handshake is clearly not production ready. However, once the handshake is performed, the rest of the code runs the same stack as the other server implementations. It should be easy to replace the HTTP interface with any asyncio aware HTTP framework.