写了一个select非阻塞的服务器端程序，但是同时启动2个客户端去连接的话会出现问题。2个客户端都可以连接成功，但是只有第二个连接的客户端发送的信息可以被正确接收到，第一个客户端发送的消息，一直出错，错误号是10035，即WSEAWOULDBLOCK，，，我很奇怪为什么会一直都无法接收。还有很多其他的问题，不一一叙述，我没自己写客户端程序，使用的是TCP&UDP测试工具进行测试的

WSADATA Wsadata;
	SOCKET Server;
	SOCKET Client;
	SOCKADDR_IN serverAddr;
	SOCKADDR_IN clientAddr;
	//保存所有客户端socket的数组
	vector<SOCKET> clientSockets;
	int index = 0;

	FD_SET ReadSet;
	//初始化环境
	if (WSAStartup(MAKEWORD(2, 1), &Wsadata) != 0)
	{
		fprintf(stderr, "Init socket failed, error: %d\n", GetLastError());
		WSACleanup();
		return -1;
	}

	Server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (Server == INVALID_SOCKET)
	{
		fprintf(stderr, "Create socket failed, error: %d\n", GetLastError());
		closesocket(Server);
		WSACleanup();
		return -1;
	}
	//设置为非阻塞模式
 	unsigned long mode = 1;
 	if (ioctlsocket(Server, FIONBIO, &mode) != 0)
	{
		return -1;
	}
	//设置
	serverAddr.sin_family = AF_INET;
	serverAddr.sin_port = htons(8888);
	serverAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	//绑定
	int ret = bind(Server, (SOCKADDR*)&serverAddr, sizeof(SOCKADDR_IN));
	if (ret != 0)
	{
		fprintf(stderr, "Bind socket failed, error: %d\n", GetLastError());
		closesocket(Server);
		WSACleanup();
		return -1;
	}
	printf("绑定成功...\n");
	//监听
	ret = listen(Server, 10);
	if (ret != 0)
	{
		fprintf(stderr, "listen socket failed, error: %d\n", GetLastError());
		closesocket(Server);
		WSACleanup();
		return -1;
	}
	printf("启动监听...\n");
	while (1)
	{
		struct timeval tv;
		tv.tv_sec = 2;
		tv.tv_usec = 0;
		FD_ZERO(&ReadSet);
		for (int i = 0; i < index; i++)
		{
			//将所有的客户端放入集合中
			FD_SET(clientSockets[i], &ReadSet);
		}
		//将服务器的socket放入集合中
		FD_SET(Server, &ReadSet);

		if (select(0, &ReadSet, NULL, NULL, &tv) == SOCKET_ERROR)
		{
			fprintf(stderr, "select error: %d\n", GetLastError());
			closesocket(Server);
			WSACleanup();
			return -1;
		}
		if (FD_ISSET(Server, &ReadSet))
		{
			int len = sizeof(clientAddr);
			//接收
			Client = accept(Server, (SOCKADDR*)&clientAddr, &len);
			if (Client != INVALID_SOCKET)
			{
				//将已经连接的客户端保存到数组中
				clientSockets.push_back(Client);
				index++;
				printf("连接成功.\n");
			}
			else
			{
				continue;
			}
		}//end if
		for (int i = 0; i < clientSockets.size(); ++i)
		{
			if (FD_ISSET(clientSockets[i], &ReadSet))
			{
					Sleep(1);
					char buf[256];
					memset(buf, 0, sizeof(buf));
					int ret = recv(Client, buf, sizeof(buf)-1, 0);
					if (ret == SOCKET_ERROR)
					{
						if (GetLastError() == WSAEWOULDBLOCK)
						{
							continue;
						}
						else
						{
							fprintf(stderr, "recv error : %d\n", GetLastError());
							closesocket(clientSockets[i]);
							clientSockets[i] = NULL;
							index--;
							return -1;
						}
					}
					if (ret == 0)
					{
						closesocket(clientSockets[i]);
						clientSockets.erase(clientSockets.begin() + i);
						i--;
						index--;
						printf("断开连接.\n");
						continue;
					}
					printf("接受信息内容 :%s\n", buf);

			}//end if
		}//end for
		//将获得的消息存储在消息队列中
	}
	//关闭socket，清理环境
	closesocket(Server);
	closesocket(Client);
	WSACleanup();
	return -1;

 
        for (int i = 0; i < index; ++i)
        {
            if (FD_ISSET(clientSockets[i], &ReadSet))
            {
                    Sleep(1);
                    char buf[256];
                    memset(buf, 0, sizeof(buf));
                    int ret = recv(Client, buf, sizeof(buf)-1, 0);
                    if (ret == SOCKET_ERROR)
                    {
                        if (GetLastError() == WSAEWOULDBLOCK)
                        {
                            continue;
                        }
                        else
                        {
                            fprintf(stderr, "recv error : %d\n", GetLastError());
                            closesocket(clientSockets[i]);
                            clientSockets[i] = NULL;
                            index--;
                            return -1;
                        }
                    }
                    if (ret == 0)
                    {
                        closesocket(clientSockets[i]);
                        clientSockets.erase(clientSockets.begin() + i);
                        i--;
                        index--;
                        printf("断开连接.\n");
                        continue;
                    }
                    printf("接受信息内容 :%s\n", buf);
                     
            }//end if
        }//end for
         //put it at the end, every sockets in the vector were put into  the fd set
         if (FD_ISSET(Server, &ReadSet))
        {
            int len = sizeof(clientAddr);
            //接收
            Client = accept(Server, (SOCKADDR*)&clientAddr, &len);
            if (Client != INVALID_SOCKET)
            {
                //将已经连接的客户端保存到数组中
                clientSockets.push_back(Client);
                index++;
                printf("连接成功.\n");
            }
            else
            {
                continue;
            }
        }//end if