If there's already a listening socket on a port, then the state of the socket is changed to listen.

如果端口上已存在侦听的套接字，则将套接字的状态更改为LISTEN。

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If the socket is not a listening socket, then control falls to soclose to check if there is already a control block attached to the socket.

如果套接字不是侦听套接字，则控制开始使用soclose，以检查是否已存在附加到套接字的控制块。

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The soo_close() simply calls the so_close() function, which first checks if the socket to be closed is a listening socket (socket that's accepting incoming connections).

soo_close() 仅调用 so_close() 函数，该函数首先检查要关闭的套接字是否为侦听套接字（正在接收传入连接的套接字）。

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