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?
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@Mörre What is the problem? (English is not my native language.) – Supercactus Feb 15 '13 at 21:06
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I have been asking myself the same thing and I could not find an answer. Everybody uses 30 secs without explaining why. Nice to find your question. – silver_mx Mar 10 '19 at 01:29
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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.
Tomasz Nurkiewicz
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Thanks for your answer. So, XMLHttpRequest's readyState does not change when a TCP connection is dropped? – Supercactus Feb 15 '13 at 21:11
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@Supercactus: it should if remote server/OS closes the connection. But if you simply cut off the network cable, you might not be notified. – Tomasz Nurkiewicz Feb 15 '13 at 21:14