sl_Recv在设计成非阻塞模式的时候，没有接收到的信息时，返回什么？

如标题。

Viki Shi：

return the number of bytes received, or a negative value if an error occurred.using a non-blocking recv a possible negative value is SL_EAGAIN. SL_RET_CODE_INVALID_INPUT (-2) will be returned if fromlen has incorrect length. SL_POOL_IS_EMPTY may be return in case there are no resources in the system.In this case try again later or increase MAX_CONCURRENT_ACTIONS