c++ - 同时打开 TCP

Question

我正在实现“同步 TCP 打开”。这意味着两个对等方将同时尝试相互连接。我很困惑在这种情况下是否需要 listen。

或者告诉我每个客户端需要调用的socket顺序。

我正在为 TCP 打洞实现这个。

谢谢，

Answer 1

来自 Wikipedia's article on TCP hole punching :

Because both parties are connection TO each other (e.g. 2 x CONNECT(), no LISTEN(), ACCEPT(), etc.) to generate OUTBOUND traffic there is however a problem with:

TCP Sequence numbers

Acknowledgment numbers

The required state is just like after the three-way-handshake: Each host must have an acknowledge number == other sequence number + 1. This is achieved through Sequence and Acknowledgement Number coordination.

listen() 不是必需的。顺序取决于可用的内容。