windows VC socket，默認recv是阻塞的
int nNetTimeout=1000;//1秒，
setsockopt(m_sock, SOL_SOCKET,SO_RCVTIMEO,(char *)&nNetTimeout,sizeof(int));
int nRet = recv(m_sock................
printf("recvlen = %d, errno =%d", nRet, errno);
設定了套接字為1秒超時，當1秒超時未收到訊息時，回傳為-1，我想區分-1時候是出錯還是超時，查網上資料，說判斷errno，但我這邊errno列印一直為2, 為2好像是說什么檔案或檔案夾不存在，但這個好像是之前代碼造成的錯誤，所以說errno來判斷好像不準確。。
后來我將判斷errno改成列印WSAGetLastError()，能夠得到10060 WSAETIMEDOUT , 但是我在想如果我是多執行緒多個套接字連接了，這樣WSAGetLastError()好像也不能準確的判斷出是當前執行緒當前執行緒的套接字超時的？ 所以感覺這方法也不夠好。
那么請問要如何判斷是超時回傳-1，還是非正確的回傳-1
uj5u.com熱心網友回復：
recvThe Windows Sockets recv function receives data from a connected socket.
int recv (
SOCKET s,
char FAR* buf,
int len,
int flags
);
Parameters
s
[in] A descriptor identifying a connected socket.
buf
[out] A buffer for the incoming data.
len
[in] The length of buf.
flags
[in] A flag specifying the way in which the call is made.
Remarks
The recv function is used to read incoming data on connection-oriented sockets, or connectionless sockets. When using a connection-oriented protocol, the sockets must be connected before calling recv. When using a connectionless protocol, the sockets must be bound before calling recv.
The local address of the socket must be known. For server applications, use an explicit bind function or an implicit accept or WSAAccept function. Explicit binding is discouraged for client applications. For client applications the socket can become bound implicitly to a local address using connect, WSAConnect, sendto, WSASendTo, or WSAJoinLeaf.
For connected or connectionless sockets, this function restricts the addresses from which received messages are accepted. The function only returns messages from the remote address specified in the connection. Messages from other addresses are (silently) discarded
For connection-oriented sockets (type SOCK_STREAM for example), calling recv will return as much information as is currently available—up to the size of the buffer supplied. If the socket has been configured for in-line reception of out-of-band data (socket option SO_OOBINLINE) and out-of-band data is yet unread, only out-of-band data will be returned. The application can use the ioctlsocket or WSAIoctl SIOCATMARK command to determine whether any more out-of-band data remains to be read.
For connectionless sockets (type SOCK_DGRAM or other message-oriented sockets), data is extracted from the first enqueued datagram (message) from the destination address specified by the connect function.
If the datagram or message is larger than the buffer supplied, the buffer is filled with the first part of the datagram, and recv generates the error WSAEMSGSIZE. For unreliable protocols (for example, UDP) the excess data is lost; for reliable protocols, the data is retained by the service provider until it is successfully read by calling recv with a large enough buffer. For TCP/IP, an application cannot receive from any multicast address until after becoming a group member.
If no incoming data is available at the socket, the recv call blocks and waits for data to arrive according to the blocking rules defined for WSARecv with the MSG_PARTIAL flag not set unless the socket is nonblocking. In this case, a value of SOCKET_ERROR is returned with the error code set to WSAEWOULDBLOCK. The select, WSAAsyncSelect, or WSAEventSelect functions can be used to determine when more data arrives.
If the socket is connection oriented and the remote side has shut down the connection gracefully, and all data has been received, a recv will complete immediately with zero bytes received. If the connection has been reset, a recv will fail with the error WSAECONNRESET.
The flags parameter can be used to influence the behavior of the function invocation beyond the options specified for the associated socket. The semantics of this function are determined by the socket options and the flags parameter. The latter is constructed by or'ing the following values:
Value Meaning
MSG_PEEK Peek at the incoming data. The data is copied into the buffer but is not removed from the input queue. The function then returns the number of bytes currently pending to receive.
MSG_OOB Process out-of-band data. (See section DECnet Out-Of-band data for a discussion of this topic.)
Return Values
If no error occurs, recv returns the number of bytes received. If the connection has been gracefully closed, the return value is zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.
Error Codes
WSANOTINITIALISED A successful WSAStartup must occur before using this function.
WSAENETDOWN The network subsystem has failed.
WSAEFAULT The buf parameter is not completely contained in a valid part of the user address space.
WSAENOTCONN The socket is not connected.
WSAEINTR The (blocking) call was canceled through WSACancelBlockingCall.
WSAEINPROGRESS A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.
WSAENETRESET The connection has been broken due to the keep-alive activity detecting a failure while the operation was in progress.
WSAENOTSOCK The descriptor is not a socket.
WSAEOPNOTSUPP MSG_OOB was specified, but the socket is not stream-style such as type SOCK_STREAM, out-of-band data is not supported in the communication domain associated with this socket, or the socket is unidirectional and supports only send operations.
WSAESHUTDOWN The socket has been shut down; it is not possible to recv on a socket after shutdown has been invoked with how set to SD_RECEIVE or SD_BOTH.
WSAEWOULDBLOCK The socket is marked as nonblocking and the receive operation would block.
WSAEMSGSIZE The message was too large to fit into the specified buffer and was truncated.
WSAEINVAL The socket has not been bound with bind, or an unknown flag was specified, or MSG_OOB was specified for a socket with SO_OOBINLINE enabled or (for byte stream sockets only) len was zero or negative.
WSAECONNABORTED The virtual circuit was terminated due to a time-out or other failure. The application should close the socket as it is no longer usable.
WSAETIMEDOUT The connection has been dropped because of a network failure or because the peer system failed to respond.
WSAECONNRESET The virtual circuit was reset by the remote side executing a "hard" or "abortive" close. The application should close the socket as it is no longer usable. On a UDP datagram socket this error would indicate that a previous send operation resulted in an ICMP "Port Unreachable" message.
QuickInfo
Windows NT: Yes
Windows: Yes
Windows CE: Use version 1.0 and later.
Header: Declared in winsock2.h.
Import Library: Link with ws2_32.lib.
See Also
recvfrom, select, send, socket, WSAAsyncSelect, WSARecvEx
uj5u.com熱心網友回復：
沒人解決嗎。。。uj5u.com熱心網友回復：
試試 getsockopt level = SOL_SOCKET SO_ERRORuj5u.com熱心網友回復：
recv前先select一下 萬無一失
uj5u.com熱心網友回復：
使用 getsockopt 引數模式使用SO_ERROR轉載請註明出處，本文鏈接：https://www.uj5u.com/gongcheng/72206.html
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