A common misconception explained by Phil Leggetter:
False! HTTP 1.1 reuses TCP connections by default. This means the overhead of each real-time update via PubSubHubbub is only the HTTP headers (a minimal envelope). HTTP 1.1 is why it's possible to build a PubSubHubbub subscriber that handles hundreds of updates per second with little effort.
"The problem with [PubSubHubbub] is that for each push a new HTTP connection needs to be established and the data then needs to be transferred. Establishing a connection takes time and resources so clearly a single persistent connection is a better solution. This is where I think XMPP PubSub is a better solution."
False! HTTP 1.1 reuses TCP connections by default. This means the overhead of each real-time update via PubSubHubbub is only the HTTP headers (a minimal envelope). HTTP 1.1 is why it's possible to build a PubSubHubbub subscriber that handles hundreds of updates per second with little effort.