2009-02-19 16:14:09 +00:00
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ADC protocol extensions supported:
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STATUS: **** Not yet implemented.
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the 'AUT0' extension (network connection auto detection extension).
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Rationale: Detect if client is capable of initiating active connections.
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After logging in:
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Client -> 'HCHK 12345 ABCD'.
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Server sends a UDP packet containing token to the client's IP address at the given port as shown in the INF message.
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Server -> 'ICHK ABCD'
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The server should send it from a UDP socket bound to the same port as the TCP server, which means the server will
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have to listen to both TCP and UDP.
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If client receives the packet, it knows it can receive UDP connections, and will advertise it in the INF message as
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a supported feature.
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If the client does not receive any UDP packets within a few seconds, it MAY try to reconfigure the router using
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UPnP/ZeroConf, and issue a HCHK command to the server again.
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If the client still doesn't receive any UDP packets, hole punching can be tried.
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The server will send a UDP packet to the hub (using the port of the TCP server), and reissue the HCHK command.
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The UDP packet SHOULD be echoed by the hub.
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This UDP packet should contain simply 'HECH {cid} {token}' (Hub echo).
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The hub should send a packet containing the token back:
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2019-01-14 19:16:48 +00:00
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'IECH {token} {host:port}', as well as the same message via TCP.
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2009-02-19 16:14:09 +00:00
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If the client receives the message via UDP, it should now be able to determine the type of NAT.
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2019-01-14 19:03:07 +00:00
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If the client receives the message via TCP only it knows it has a firewall blocking incoming communication.
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2009-02-19 16:14:09 +00:00
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If the client does not receive the message, it should assume a firewall is blocking all UDP communication,
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and resume in passive mode.
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Requirements:
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'AUT0' in the extensions message (SUP) for client and hub.
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Server will also listen to UDP messages on the same port as the TCP port.
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The server MUST now respond to the 'HCHK' command via TCP
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The server MUST now respond to the 'HECH' command via UDP.
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The client will always initiate communication.
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-------------------------------------------------------------------------------
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Syntax: HCHK {port} {token}
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- port is a 16-bit port number where the client is listening for packets.
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- token is 4 bytes base32 encoded data specified by the client.
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Example:
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Client: 'HCHK 1511 BACD' (tcp)
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Server: 'ICHK BACD' (udp)
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-------------------------------------------------------------------------------
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Syntax: HECH {cid} {token}
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- cid is the client ID.
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- token is 4 bytes base32 encoded data specified by the client.
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Example:
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Client: 'HECH 3NGFVJUDBRHX2CYRJGQ5HACRDM5CTNLGZ36M64I BACD' (udp)
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Server: 'IECH BACD 192.168.0.1:1512' (udp)
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Server: 'IECH BACD 192.168.0.1:1512' (tcp)
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Security considerations:
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The hub must verify that IP address where the HECH command originated from
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matches the IP address where the user with the given CID is connected from.
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If the CID and IP does not match, or the CID is not used the hub MUST ignore
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the request.
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