非阻塞套接字-如何检查连接是否成功? [英] Non blocking socket - how to check if a connection was successful?

问题描述

正确设置了非阻塞套接字后，我将执行以下连接:

After setting up a non blocking socket correctly I do the following to connect:

1. 在套接字上调用connect.
2. 如果返回0，则表明我已经连接，否则，请检查errno.
3. 如果errno不是EINPROGRESS，则存在错误.

4. 如果errno是EINPROGRESS，我可以通过以下方式轮询连接状态:

1. Call connect on the socket.
2. If it returns 0, I have already connected, if not, check errno.
3. If errno is not EINPROGRESS there is an error.

4. if errno is EINPROGRESS I can poll the connect status by:

select_status = sock_select(FD_SETSIZE, NULL, &file_descriptor_set, NULL, &timeout);

如果select_status > 0，然后与FD_ISSET检查是否设置了文件描述符.

if select_status > 0 then check with FD_ISSET if the file descriptor is set.

那是正确的吗?我应该检查fd_write而不是fd_read吗?选择后我应该打电话给getsockopt吗?有什么争论?

Is that correct? And should I check for fd_write not fd_read? Should I call getsockopt after select? With what arguments?

我找不到需要做什么的明确解释.

I cannot find a clear explanation of what needs to be done.

我确实连接了，但是我的程序未正确报告它，所以我错误地使用了select，或者是因为我没有检查getsockopt.

I do connect but my program is not reporting it correctly so I am using select wrong or it is because I don't check getsockopt.

什么告诉我建立了连接?

What tells me that the connection was made?

推荐答案

1. 在套接字上调用connect.
2. 如果返回0，则表明我已经连接，否则，请检查errno.
3. 如果errno不是EINPROGRESS，则出现错误.

1. Call connect on the socket.
2. If it returns 0, I have already connected, if not, check errno.
3. If errno is not EINPROGRESS there is an error.

以上所有内容都是正确的(Windows除外，您需要检查WSAEWOULDBLOCK而不是EINPROGRESS).

All of the above is correct (except under Windows you'd need to check for WSAEWOULDBLOCK instead of EINPROGRESS).

1. 如果errno是EINPROGRESS，我可以通过以下方式轮询连接状态:select_status = sock_select(FD_SETSIZE，NULL，& file_descriptor_set，NULL，& timeout);如果select_status> 0，则检查FD_ISSET是否设置了文件描述符.

正确(假设sock_select()与select()是一样的东西)，不同之处在于FD_SETSIZE应该是您正在观看的所有文件描述符值的最大值加1.

Correct (assuming sock_select() is the same thing as select()), except that FD_SETSIZE should be the maximum value of all the file-descriptor values you are watching, plus 1.

那是正确的吗?我应该检查fd_write而不是fd_read吗?

Is that correct? And should I check for fd_write not fd_read?

对.

什么告诉我建立了连接?

What tells me that the connection was made?

异步连接操作完成后，select()将返回，并且FD_ISSET(theSocket，& writeSet)将返回true.

When the async-connection-operation has completed, select() will return and FD_ISSET(theSocket, &writeSet) will return true.

发生这种情况时，您需要确定连接尝试是成功还是失败.这是我为此使用的功能:

When that happens, you need to find out if the connection attempt succeeded or failed. Here's a function I use for that:

// Returns true if the async connection on (fd) is connected; false if it failed
bool DidTheAsyncTCPConnectionSucceed(int fd)
{
   struct sockaddr_in junk;
   socklen_t length = sizeof(junk);
   memset(&junk, 0, sizeof(junk));
   return (getpeername(fd, (struct sockaddr *)&junk, &length) == 0);
}

如果返回true，则说明您的套接字已连接并可以正常使用.如果返回false，则表明异步连接失败，您应该关闭套接字并以某种方式处理该失败.

If that returns true, your socket is connected and ready to use in the normal ways. If it returns false, the async-connection failed and you should close() the socket and handle that failure somehow.

(同样，在Windows下，行为略有不同；在Windows下，如上所述，获得有关连接成功的通知的工作原理，但是如果您想获得有关连接失败的通知，则需要观看exception-fd在Windows中，当异步TCP连接失败时，会通知您FD_ISSET(fd，& exceptionSet).

(Again there is a slightly different behavior under Windows; under Windows, getting notified about the connection succeeding works as described above, but if you want to be notified about the connection failing, you'll need to watch the exception-fd-set as well. Under Windows, FD_ISSET(fd, &exceptionSet) is what will notify you when the asynchronous TCP connection failed).

这篇关于非阻塞套接字-如何检查连接是否成功?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！