Why setting a client-side timeout when using long

问题:

In almost every long polling examples I see, there is something like a timeout of 30 seconds client-side. What is the precise reason for this?

回答1:

Some routers, proxies or whatever device there is in the middle might decide to drop TCP/IP connections being idle for extensive period of time. Also refreshing connection once in a while makes sure you'll discover server failure quicker.