套接字通信中send()和recv()的行为
以下是设置：
Server Client
| |
accept connect
| |
v |
send msg1-> |
| |
v v
recv <- send
| |
v v
send msg2-> recv
| |
v v
close这是我的问题：
1.客户端在关闭之前其实就收到了msg1，为什么会这样？
2.发送msg2正常返回。既然客户端收到msg1后就关闭了，为什么发送msg2成功呢？
PS 我正在使用 TCP 流套接字。
The following is the setup:
Server Client
| |
accept connect
| |
v |
send msg1-> |
| |
v v
recv <- send
| |
v v
send msg2-> recv
| |
v v
closeHere is my question:
1. Client actually receives msg1 before it closes, why is it like this?
2. send msg2 returns normally. Since client closes after receiving msg1, why is send msg2 successful?
P.S. I'm using stream socket for TCP.
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recv 函数将获取接收缓冲区中的下一个内容。对于客户端来说，如果套接字是数据报套接字，那么接下来是msg1。如果它是一个流套接字，则不会维护消息边界，因此如果 msg2 已到达并且在那里，recv 可能包含来自 msg1 和 msg2 的数据在recv 缓冲区中为两者提供了空间。
send不会等待对方recv消息，它只是将其添加到发送队列中。此时它不知道客户端是否会在读取连接之前关闭连接。如果您需要知道应该让客户端发送响应来确认消息。The
recvfunction will get whatever is next in the receive buffer. In the case of the client, if the socket is a datagram socket, what is next is msg1. If it is a stream socket then message boundaries are not maintained so the recv could include data from both msg1 and msg2 if msg2 has arrived and there is room for both in the recv buffer.senddoes not wait for the other side torecvthe message, it just adds it to the send queue. It does not know at that point whether the client will close the connection before reading it. If you need to know that you should have the client send a response to acknowledge the message.连接建立后，操作系统管理进入和离开系统的数据包，recv() 调用仅读取数据包缓冲区，send() 调用仅对数据包进行排队。
After your connection is set up, the OS manages the packets entering and leaving your system, the recv() call just reads the packet buffer, and the send() call just queues the packets.