C语言 错误：11，资源暂时不可用
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Errno: 11, Resource Temporarily Unavailable
提问by rharrison33
I am using c sockets to implement a reliable UDP protocol. I am using the following code to set a timeout on a socket in which I'm waiting for an acknowledgement. I am not sure why I am getting errno 11, resource temporarily unavailable.
我正在使用 c 套接字来实现可靠的 UDP 协议。我正在使用以下代码在等待确认的套接字上设置超时。我不确定为什么我会收到 errno 11，资源暂时不可用。
//set timer for recv_socket
struct timeval tv;
tv.tv_usec = TIMEOUT_MS;
if(setsockopt(rcv_sock, SOL_SOCKET, SO_RCVTIMEO,&tv,sizeof(tv)) < 0){
printf("Error setting the socket timeout.\n");
}
int recv_msg_len;
if(recv_msg_len = recvfrom(rcv_sock, ackBuffer,sizeof(ackBuffer), 0,
(struct sockaddr *) &servAddr2, &fromSize) < 0){
//timeout reached
printf("Error Reporting: %d : %s\n", errno, strerror(errno));
num_timeouts++;
}
I have also tried the select method that was mentioned in the comments. I have the following code inside a loop, but the recvfrom never times out.
我也尝试过评论中提到的 select 方法。我在循环中有以下代码，但 recvfrom 永远不会超时。
fd_set set;
FD_ZERO(&set); /* empties the set */
FD_CLR(rcv_sock,&set); /* removes FD from the set */
FD_SET(rcv_sock,&set); /* adds FD to the set */
if(select(rcv_sock + 1, &set, NULL, NULL, &tv) < 0){
printf("\nError Reporting: %d : %s\n\n", errno, strerror(errno));
return -1;
}
if(!FD_ISSET(rcv_sock,&set)){ /* true if FD is in the set */
printf("socket is not set properly.\n");
}
回答by alk
When calling recvfrom()on a blocking socket and a time out had been set using setsockopt()it is normal to get the error EAGAIN (11)in case the call to recvfrom()timed out (that is: no data was received in the time period specified as time out).
当调用recvfrom()阻塞套接字并使用超时设置时，如果调用超时（即：在指定为超时的时间段内没有接收到数据），setsockopt()通常会出现错误。EAGAIN (11)recvfrom()
Verbatim from man recvfrom:
逐字来自man recvfrom：
RETURN VALUE
...
ERRORS
... .
EAGAIN or EWOULDBLOCK The socket is marked non-blocking and the receive operation would block, or a receive timeout had been set and the timeout expired before data was received. ...
返回值
...
错误
……
EAGAIN 或 EWOULDBLOCK 套接字被标记为非阻塞并且接收操作将阻塞，或者已经设置了接收超时并且超时在接收数据之前到期。...
To get around this: Just call recvfrom ()again ... ;-)
要解决此问题：只需recvfrom ()再次致电...;-)
回答by user3704779
For me, the problem was due to ipV6 packets arriving on a UDP socket bound to a particular port. These were triggering the select() but when I tried to read them using recvfrom() the call returned "Resource temporarily unavailable". I don't need IPV6 for my application so I simply disabled it via sysctl.conf. Problem now gone away!
对我来说，问题是由于 ipV6 数据包到达绑定到特定端口的 UDP 套接字。这些正在触发 select() 但是当我尝试使用 recvfrom() 读取它们时，调用返回“资源暂时不可用”。我的应用程序不需要 IPV6，所以我只是通过 sysctl.conf 禁用它。现在问题消失了！
