Question

我正在构建一个在线游戏客户端，当我尝试连接到离线服务器时，我的客户端冻结，因此我想使用适合游戏的非阻塞套接字，因为在连接到服务器时还需要完成其他任务

使用非阻塞套接字时，无论结果如何，connect函数始终返回相同的值，因此此处的人员建议使用select函数查找连接请求的结果。

（在连接前设置非阻塞套接字）

u_long iMode=1;
ioctlsocket(hSocket,FIONBIO,&iMode);

（设置套接字集）

FD_ZERO(&Write);
FD_ZERO(&Err);
FD_SET(hSocket, &Write);
FD_SET(hSocket, &Err);

TIMEVAL Timeout;

int TimeoutSec = 10; // timeout after 10 seconds
Timeout.tv_sec = TimeoutSec;
Timeout.tv_usec = 0;
int iResult = select(0,     //ignored
                     NULL,      //read
                     &(client.Write),    //Write Check
                     &(client.Err),      //Error Check
                     &Timeout);

if(iResult)
{
}
else
{
    message_login("Error","Can't connect to the server");
}

select函数总是返回-1，为什么？

Answer 1

当select()返回-1（SOCKET_ERROR）时，请使用WSAGetLastError()找出失败的原因。

如果套接字在Err退出时select()设置，请使用getsockopt(SOL_SOCKET, SO_ERROR)检索套接字错误代码，告诉您connect()失败的原因。

对于任何非零值，

if(iResult)的计算结果为true，包括-1。您需要使用if(iResult > 0)，因为iResult将报告在任何 fd_set中发出信号的套接字数量，超时时为0，失败时为-1

尝试更像这样的东西：

u_long iMode = 1;
if (ioctlsocket(hSocket, FIONBIO, &iMode) == SOCKET_ERROR)
{
    int errCode = WSAGetLastError();
    // use errCode as needed...
    message_login("Error", "Can't set socket to non-blocking, error: ..."); // however you supply a variable value to your message...
}

if (connect(client.hSocket, ...) == SOCKET_ERROR)
{
    int errCode = WSAGetLastError();
    if (errCode != WSAEWOULDBLOCK)
    {
        // use errCode as needed...
        message_login("Error", "Can't connect to the server, error: ..."); // however you supply a variable value...
    }
    else
    {
        // only in this condition can you now use select() to wait for connect() to finish...
    }
}

TIMEVAL Timeout;

int TimeoutSec = 10; // timeout after 10 seconds
Timeout.tv_sec = TimeoutSec;
Timeout.tv_usec = 0;

int iResult = select(0,     //ignored
                     NULL,      //read
                     &(client.Write),    //Write Check
                     &(client.Err),      //Error Check
                     &Timeout);

if (iResult > 0)
{
    if (FD_ISSET(client.hSocket, &(client.Err)))
    {
        DWORD errCode = 0;
        int len = sizeof(errCode);
        if (getsockopt(client.hSocket, SOL_SOCKET, SO_ERROR, (char*)&errCode, &len) == 0)
        {
             // use errCode as needed...
             message_login("Error", "Can't connect to the server, error: ..."); // however you supply a variable value to your message...
        }
        else
            message_login("Error", "Can't connect to the server, unknown reason");
    }
    else
        message_login("Success", "Connected to the server");
}
else if (iResult == 0)
{
    message_login("Error", "Timeout connecting to the server");
}
else
{
    int errCode = WSAGetLastError();
    // use errCode as needed...
    message_login("Error", "Can't connect to the server, error: ..."); // however you supply a variable value to your message...
}

在非阻塞套接字中选择功能

1 个答案: