WinSocket的问题:非阻塞模式recv返回-1,WSAGetLastError 返回 0

重新注册 2017-01-12 11:27:41

尝试非阻塞的socket编程，碰到WSAGetLastError()一直是返回值为0的问题，百度了几个博客，都说是因为WSAGetLastError()的调用必须及时，不能被其他的系统调用隔开，否则得到的错误值被掩盖。
如博客： http://blog.csdn.net/tianbaowen/article/details/8485567
然而，我的代码在recv()后紧跟着的系统调用就是WSAGetLastError(),却依然得到的是返回值0。最后上了国外的网站看，有人说是需要直接调用GetLastError()就可以，结果一改，果然就得到了10035，现在还不知道为何。。。



DWORD IniSOCKDLL()

{

	WORD wVersionRequested;

	WSADATA wsaData;

	int err=0;



	wVersionRequested = MAKEWORD( 2, 2 );

	err = WSAStartup( wVersionRequested, &wsaData ); 

	if(err != 0)

		return err;

	if ( LOBYTE( wsaData.wVersion ) != 2 ||

		HIBYTE( wsaData.wVersion ) != 2 ) {

		WSACleanup( );

		err = -1;

	}

	return err;

}



int main()

{

	int status;

	IniSOCKDLL();

	SOCKET sc=socket(AF_INET,SOCK_STREAM,0);

	

	SOCKADDR_IN addr;

	int len;

	addr.sin_family=AF_INET;

	addr.sin_addr.s_addr = inet_addr("127.0.0.1");

	addr.sin_port = htons(21050);

	len = sizeof(addr);

	cout << "start client" << endl;

	status = ::connect(sc, (struct sockaddr *)&addr, len);//server已开启，连接server端



	char buff[1024];

	ZeroMemory(buff,1024); 

	memcpy(buff,"linking",7);





	u_long iMode = 1;//非阻塞模式

	ioctlsocket(sc, FIONBIO, &iMode);//设置套接字sc为非阻塞模式

	len = send(sc,buff, strlen(buff),0);

	while(!quit){

		len = recv(sc, buff, 1024, 0);

		if(len < 0){

			int err = GetLastError();//改成这个就好使； 用WSAGetLastError()就一直是0

			if(err == WSAENETDOWN || err == WSAECONNRESET || err == WSAENOTCONN){//断线重连

				closesocket(sc);

				sc = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, NULL);

				int status = ::connect(sc, (struct sockaddr *)&addr, sizeof(addr));

				if(status < 0){

					Sleep(3000);

				}else{

					memcpy(buff,"linking",7);

					ioctlsocket(sc, FIONBIO, &iMode);

					send(sc,buff,7,0);

				}

			}else if(err == WSAEWOULDBLOCK){

				Sleep(10);

			}

			continue;

		}

		send(sc, "received", strlen("received"), 0);

		if(strncmp(buff,"left",4) ==0){

			cout << "left" << endl;

		}else if(strncmp(buff,"right",5)==0){

			cout << "right" << endl;

		}

		ZeroMemory(buff, 1024);



	}//while



	closesocket(sc);

	cout << "stopped..." << endl;

        return 0;

}