The switch in the tcp_usrreq function calls in_setpeeraddr(), which copies the foreign IP address and foreign port number from the protocol control block and returns these to the server process.

tcp_usrreq 函数中的切换调用 in_setpeeraddr()，后者从协议控制块复制外来 IP 地址和外来端口号，并将其返回到服务器进程。

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The control now returns to the connect function, which sleeps until the protocol layer wakes up-indicating that the connection is now ESTABLISHED or that there has been an error on the socket.

控制现在返回到connect函数，该函数处于睡眠状态，直到协议层唤醒—指示连接现在是ESTABLISHED，或套接字上存在错误。

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The core function of transport protocol is to provide end-to-end reliability and flow control.

传输协议的核心功能是提供端-端可靠性和流量控制。

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