You need to either send an HTTP/1.1 request, or HTTP/1.0 with the appropriate headers
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HTTP/1.1 does not automatically keep the connection open. An appropriate Keep-Alive header must be sent.
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Keep-Alive was introduced in HTTP/1.1. HTTP/1.0 does not support keeping the connection open.
However, since Keep-Alive is compatible with HTTP/1.0, many servers that claim to be HTTP/1.0 support Keep-Alive. This was the cases even when HTTP/1.1 was still a draft.
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Finally, servers are under no requirement to honour Keep-Alive requests.
