c - send() 总是发送整个缓冲区吗？

Question

send() 应返回发送的字节数或错误代码，但我发现的所有示例仅检查错误代码，而不检查发送的字节数。

//typical example
int cnt=send(s,query,strlen(query),0);
if (cnt < 0) return(NULL);
//Hey, what about cnt < strlen(query)?

Answer 1

问:“send()”总是返回整个缓冲区吗？

答:不一定。

来自 Beej 的指南: * http://beej.us/guide/bgnet/html/multi/syscalls.html#sendrecv

send() returns the number of bytes actually sent out—this might be less than the number you told it to send! See, sometimes you tell it to send a whole gob of data and it just can't handle it. It'll fire off as much of the data as it can, and trust you to send the rest later. Remember, if the value returned by send() doesn't match the value in len, it's up to you to send the rest of the string. The good news is this: if the packet is small (less than 1K or so) it will probably manage to send the whole thing all in one go. Again, -1 is returned on error, and errno is set to the error number.

问:“recv()”是否总是读取整个缓冲区？

答:不，绝对不是。您永远不要假设您收到的缓冲区是“整个消息”。或者假设您收到的消息来自一个，单个消息。

这是一个很好的简短解释。它适用于 Microsoft/C#，但适用于所有 套接字 I/O，使用任何语言:

• http://blogs.msdn.com/b/joncole/archive/2006/03/20/simple-message-framing-sample-for-tcp-socket.aspx