插座选择失败，并在正在进行的操作 - 非阻塞模式 [英] socket select fails with operation in progress - Non blocking mode

问题描述

我们的应用程序使用与连接和选择操作（C code）一个非阻塞套接字的使用。
该pusedo code是如下

Our application uses a non-blocking socket usage with connect and select operations (c code). The pusedo code is as below

unsigned int ConnectToServer(struct sockaddr_in *pSelfAddr,struct sockaddr_in *pDestAddr)
{
    int sktConnect = -1;

    sktConnect = socket(AF_INET,SOCK_STREAM,0);
    if(sktConnect == INVALID_SOCKET)
        return -1;


    fcntl(sktConnect,F_SETFL,fcntl(sktConnect,F_GETFL) | O_NONBLOCK);
    if(pSelfAddr != 0)
    {
        if(bind(sktConnect,(const struct sockaddr*)(void *)pSelfAddr,sizeof(*pSelfAddr)) != 0)
        {
            closesocket(sktConnect);
            return -1;
        }
    }


    errno = 0;
    int nRc = connect(sktConnect,(const struct sockaddr*)(void *)pDestAddr, sizeof(*pDestAddr));
    if(nrC != -1)
    {
        return sktConnect;
    }

    if(errno != EINPROGRESS)
    {
        int savedError = errno;
        closesocket(sktConnect);
        return -1;
    }

    fd_set scanSet;
    FD_ZERO(&scanSet);
    FD_SET(sktConnect,&scanSet);

    struct timeval waitTime;
    waitTime.tv_sec = 2;
    waitTime.tv_usec = 0;

    int tmp;
    tmp = select(sktConnect +1, (fd_set*)0, &scanSet, (fd_set*)0,&waitTime);
    if(tmp == -1 || !FD_ISSET(sktConnect,&scanSet))
    {
        int savedErrorNo = errno;
        writeLog("Connect %s failed after select, cause %d, error %s",inet_ntoa(pDestAddr->sin_addr),savedErrorNo,strerror(savedErrorNo));
        closesocket(sktConnect);
        return -1;
    }

    .   
    .   
    .
    .
    .}  

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问题陈述结果
在上面的code时，选择失败错误code 115 这是工作正在进行中。我没有看到任何文件，选择与错误号115 失败。

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Problem statement
In the above code, the select fails with error code 115 which is "Operation in progress". I do not see any documentation on select failing with errno 115.

一个。什么时候选择失败错误code 115 在非阻塞套接字？在什么样的情况？结果
湾我们看到的这暗示了该问题的系统日志。只是我们关注我 - 我无法找到任何记录功能，它描述了这样的问题。

a. When does the select fails with error code 115 in non-blocking socket? Under what scenario?
b. Do we see any system logs which hints at this problem. Only concern for us me - I could not find any documented feature which describes such problem.

PS：我们正在使用的SUSE Linux 11企业版

PS : We are using SUSE Linux 11 Enterprise Edition.

推荐答案

的 在code的几点思考：的搜索

Some thoughts on your code:

我想下面的选择你的条件可以修改为只检查，看看，如果选择返回的值大于0，如果是这样的话，你可以检查的getsockopt的输出插座（为SOL_SOCKET和SO_ERROR）选项​​（的getsockopt（... SOL_SOCKET，SO_ERROR，...，...））查看是否连接还没有失败。

I think your condition below the select can be modified to check only to see, if select has returned a value greater than 0 and if that is the case, you can check output of getsockopt for the socket (for SOL_SOCKET and SO_ERROR) options (getsockopt(...,SOL_SOCKET, SO_ERROR,...,...)) to see if connect has not failed.

我不是很肯定，如果选择将始终返回插座为可写在连接成功的情况下。所以，你的情况，它可能（只可以）是，TMP变量不是-1，它是显示错误号是previous的连接调用错误号的情况。

I am not very sure if the select will always return the socket as writable in case of a connection success. So, in your case, it may (only may) be the case that, the tmp variable is not -1 and the errno it is showing is the errno of the previous connect call.

的 其他原因：的

Additional Reasons:

另一个很好的理由是，目的地址为您正在连接要么无法访问，或者没有一个服务器在指定的地址+端口的组合等。在这种情况下，你可以用一个阻挡套接字一次尝试，看看是否能连接。

Another good reason is that, the destination address to which you are connecting is either not reachable, or doesn't have a server waiting at the specified address + port combination. In which case, you can try once with a blocking socket to see if that connects.

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