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Server-Sent Events (SSE) provide a one-way channel for text messages from server to client over an HTTP connection. SSE provides reliability by automatically reconnecting, after a defined backoff period, in the event of a broken connection. The protocol provides identifie identified message types (channels). 

Concerns

• Requires a multithreaded server since the connection is persistent. Bottle supports several servers, and we likely would use CherryPy.

WebSockets

The WebSocket (RFC 6455) protocol provides full-duplex (two-way), message-based communications over a single TCP socket. Messages may be text or binary. It is designed for a web application, including initialization via an HTTP Upgrade header so the protocol may coexist on the HTTP port.  At the same time, as a messaging tool, it allows other two-way messaging protocols to run on top of it. See the Messaging and Queueing topic below. Due to its close relationship to HTTP and its flexibility, we expect it to become widely adopted. It already is supported in the latest versions of the well known browsers.

Concerns

• Incompatibility with firewalls and proxies. We suspect these issues eventually will be ironed out, but that may take a long time.
• Session maintenance – how to reestablish a connection if necessary?

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