用C超时实施TFTP [英] Timeout implementation in C for TFTP

问题描述

我想实现我的C实现TFTP的超时机制，我找一些一般帮助。

I am trying to implement the the timeout mechanism in my c implementation of TFTP, and i am looking for some general help.

我想知道是如何管理超时的情况。我使用了premature超时机制与信号/报警功能，但不知何故，我被困在如何处理我的超时，即如果数据包（ACK或数据）失手发生超时怎么送回来previous包或应答至服务器。

What I am wondering is how to manage the timeout situation. The premature timeout mechanism that I used is with signal/alarm functions, but somehow I am stuck in how to handle my timeouts, that is if the packet (ack or data) is missed and a timeout occurs how to send back the previous packet or ack to the server.

推荐答案

避免信号和报警如果可能的话。

Avoid signal and alarm if possible.

要么使用<一个href=\"http://forums.$c$cguru.com/showthread.php?353217-example-of-SO_RCVTIMEO-using-setsockopt%28%29\"相对=nofollow> SO_RCVTIMEO 套接字选项或只使用有选择 T秒超时。

Either use SO_RCVTIMEO socket option or just use select with a timeout of T seconds.

如果选择（）调用返回，你的插口是不是在读集，或者如果与超时错误recvfrom的回报，那么你可以采取适当的行动，你的code。

If the select() call returns and your socket is not in the read set, or if recvfrom returns with a timeout error, then you can take appropriately action in your code.

超时使用示例：

timeval tv = {0,0};
tv.tv_sec = 5;
socklen_t optionlength = sizeof(tv);
setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &tv, optionlength);

while (1)
{
    result = recvfrom(s, buffer, bufferlength, 0);
    if (result == -1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)) )
    {
       // handle timeout
    }
    else if (result == -1)
    {
       // handle critical error
    }
    else
    {
       // process next packet
    }
}

选择使用示例：

while (1)
{
    timeval tv = {0,0};
    tv.tv_sec = 5;
    fd_set readset = {};
    FD_ZERO(&readset);
    FD_SET(s, &readset);

    select(s+1, &readset, NULL, NULL, &tv);

    if (FD_ISSET(s, &readset))
    {
        result = recvfrom(s, buffer, bufferlength, 0);
        if (result == -1)
        {
            // handle error
        }
        else
        {
            // process packet
        }
    }
    else
    {
       // handle timeout
    }

}

这篇关于用C超时实施TFTP的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！