问题描述
我目前正在尝试通过Internet发送UDP消息，并且必须为端点A和B(都位于NAT之后)设置防火墙.为此，我想通过STUN服务器使用打孔.
I'm currently trying to send UDP messages over the internet and have to set up the firewalls for both endpoints A and B (which are both behind a NAT). To do this, I want to use hole punching using a STUN server.
当A向STUN服务器创建请求时(例如，私有:85.1.1.12:6000，公共:173.194.78.127:19302)，我得到85.1.1.12:6000作为响应.如果我要将数据包从相同的原始配置(用于STUN请求的原始IP和端口)发送到任何其他目标地址(目标端口保持不变)，那么我的NAT将再次更改公用端口( (从6000到其他).我发现对两个不同的STUN服务器请求使用相同的地址端口配置(两个请求都使用端口19302).
When A creates a request to the STUN server (say, private: 85.1.1.12:6000 and public: 173.194.78.127:19302) I get 85.1.1.12:6000 as a response. If I were to send a packet from the same origin configuration (same origin ip and port that were used for the STUN-request) to any other destination address (the destination port stays the same) then my NAT would change the public port again (from 6000 to anything else). I found out by using the same address-port configuration for two different STUN server requests (using port 19302 for both requests).
像这样，我无法知道将数据包发送到B时我的NAT转换了哪个端口(B无法接收任何东西，因为它的防火墙未设置).
Like this, I have no possibility of knowing what port my NAT does the translation when sending a packet to B (B can't receive anything because its firewall is not set up).
这是因为我的NAT类型与打孔不兼容，还是我弄错了概念?
Is this because my NAT type is not compatible for hole punching or did I get the concept wrong?
谢谢！
推荐答案
85.1.1.12:6000不是您的私有IP地址.它是您NAT的公共/外部IP:端口.专用IP是您的PC/设备的接口地址.
85.1.1.12:6000 is not your private IP address. Its your NAT's public/external IP:Port. Private IP is your PC/Device's interface address.
根据您的情况，我猜您有一个对称NAT.在对称NAT中，每次将某些数据包发送到另一个目标时，NAT的公共端口都会更改.如果您的目的地保持不变，那么NAT的公共IP:端口也将保持不变.
From your scenario I am guessing you have a symmetric NAT. In Symmetric NAT, your NAT's public port changes every time you send some packets to a different destination. If your destination remains same then the NAT's public IP:Port also remains same.
对于其他类型的NAT，如果您的私有IP不变，那么无论您将数据包发送到哪里，您的NAT公用IP:port(在您的情况下为85.1.1.12:6000)都将保持不变.
For other types of NAT if your private IP doesn't change then it doesn't matter where you send your packets, your NATs public IP:port (in your case 85.1.1.12:6000) will remain same.
如果一侧具有**对称NAT，而另一侧具有对称/PRC NAT，则无法进行孔打孔.
Hole punching is not possible if one side has **Symmetric NAT and other side has Symmetric/PRC NAT.
**通过对称NAT，我的意思是对称NAT，它提供了随机的端口分配.
**By Symmetric NAT I mean Symmetric NAT which gives random port allocation.
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