Return Values
If no error occurs, send returns the total number of bytes sent, which can be less than the number indicated by len. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.
无论是异步还是同步
当send成功返回时,应该可以删除缓冲区。
如果系统缓冲区满时,则send发送失败,且WSAGetLastError将返回
WSAENOBUFS
10055
No buffer space available.
An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.