Here is how htc sends data to the destination:
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Open TCP connection to hts
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Send HTTP POST with a large Content-Length
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Send TUNNEL_DATA packets until POST Content-Length would be exceeded.
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Send TUNNEL_PADDING packets to exactly satisfy Content-Length - 1
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Send TUNNEL_DISCONNECT (1 byte)
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Close TCP connection
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Go to step 1
Here is how htc gets data from the destination.
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Open TCP connection to hts
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Send HTTP GET
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Wait for response from hts
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Read TUNNEL_DATA, then TUNNEL_PADDING, TUNNEL_DISCONNECT packets
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Close TCP connection
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Go to step 1
Tunnel creation and destruction
This can be useful for users behind restrictive firewalls. If WWW access is allowed through a HTTP proxy, it's possible to use httptunnel and, say, telnet or PPP to connect to a computer outside the firewall.
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Amarjit Singh
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