punchthrough success rates is based on what kind of algorithm the
Full cone NAT: Accepts any datagrams to a port
that has been previously used. Will accept the first datagram from the
Address-Restricted cone NAT: Accepts datagrams
to a port as long as the datagram source IP address is a system we have
already sent to. Will accept the first datagram if both systems send
simultaneously. Otherwise, will accept the first datagram after we have
sent one datagram.
Port-Restricted cone NAT: Same as
address-restricted cone NAT, but we had to send to both the correct
remote IP address and correct remote port. The same source address and
port to a different destination uses the same mapping.
Symmetric NAT: A different port is chosen for
every remote destination. The same source address and port to a
different destination uses a different mapping. Since the port will be
different, the first external punchthrough attempt will fail. For this
to work it requires port-prediction (MAX_PREDICTIVE_PORT_RANGE>1)
and that the router chooses ports sequentially.
||Full cone NAT
||Address-Restricted cone NAT
||Port-Restricted cone NAT
|Full cone NAT
|Address-Restricted cone NAT
|Port-Restricted cone NAT
The NatTypeDetection plugins allow you to determine which type of NAT
you have, and therefore if NAT punchthrough is likely to complete or
not. This can be determined in advance of joining a game.
- Client opens two ports on the same IP address. In NatTypeDetectionClient, the RakNet socket is the first port, c2 is the socket on the second port, created in NatTypeDetectionClient::DetectNATType()
- Server opens two ports on one IP address, and one port on three
additional IP addresses. This is done in NatTypeDetectionServer::Startup(). The first port on the first IP address is the normal RakNet socket. The second port on the first IP address is s1p2. The other three addresses are bound to the sockets s2p3, s3p4, and s4p5.
- Client connects to the server on the first IP address normally
- Client requests NAT type detection begins
- Server attempts to send to client's second port. This was a port that was never opened previously on the client, therefore if received, then
the client is not behind a NAT. This is done in NatTypeDetectionServer::Update(), defined by STATE_TESTING_NONE_1 and STATE_TESTING_NONE_2. The reason for 2 attempts is that every attempt occurs twice. The time for each attempt is the ping * 3 + 50 milliseconds. s4p5 is used for this.
- Server sends from a different IP address to client's first port, the port that RakNet is connected on.
If received, then the client will accept datagrams from any source IP address to a port already in use. This is therefore full-cone NAT. s2p3 is used for this.
- Server sends from the second port on the already-connected IP
address, s1p2. If received, then the client is using address-restricted cone
- Client sends to another IP address on the server, from its first
(already connected) port. If the IP address and port is the same, then
the client uses the same external IP address and port to all connections
from the same source address. This is port-restricted NAT.
- Else symmetric NAT.
- Create an instance of the plugin: NatTypeDetectionServer
- Attach the plugin to an instance of RakPeerInterface: rakPeer->AttachPlugin(&nayTypeDetectionClient);
- Connect to the server, and wait for
ID_CONNECTION_REQUEST_ACCEPTED. Use the following line to use the free
server provided by RakNet: rakPeer->Connect("188.8.131.52",
60481, 0, 0);
- Call DetectNATType with the SystemAddress of the server.
- Wait for ID_NAT_TYPE_DETECTION_RESULT
- Byte 1 contains the type of NAT that you have. See the
enumeration NATTypeDetectionResult in NATTypeDetectionCommon.h
- Various utility functions are provided for this enumeration: CanConnect(), NATTypeDetectionResultToString(),
- Host a server somewhere, not using NAT / e.g. behind a
firewall. (RakNet provides a free one at 184.108.40.206:60481, however you
may wish to host your own for consistent uptime). The server must have
enough external IP addresses, as described in NAT Type Detection
- Create an instance of the plugin: NatTypeDetectionServernatTypeDetectionServer;
- Attach the plugin: rakPeer->AttachPlugin(&natTypeDetectionServer);
- Get a list of IP addresses on your system
MAXIMUM_NUMBER_OF_INTERNAL_IDS ][ 16 ];
unsigned int binaryAddresses[MAXIMUM_NUMBER_OF_INTERNAL_IDS];
SocketLayer::Instance()->GetMyIP( ipList, binaryAddresses );
- Call natTypeDetectionServer.Startup(ip2,ip3,ip4);
// ip2,ip3,ip4 must be ip addresses not already in use. If you bound
RakNet to ip1 in the call to RakPeer::Startup(), then use the 2nd to 4th
indices in ipList.
See the sample \Samples\NATCompleteClient