如何找出为什么ssh会话不退出有时？ [英] How to figure out why ssh session does not exit sometimes?

问题描述

我有一个C ++应用程序使用ssh来召集到服务器的连接。我发现有时ssh会话在命令召唤服务器已经退出之后很久。看看Centos4的ssh页面，我看到以下内容：

I have a C++ application that uses ssh to summon a connection to the server. I find that sometimes the ssh session is left lying around long after the command to summon the server has exited. Looking at the Centos4 man page for ssh I see the following:

 The session terminates when the command or shell on the remote machine
 exits and all X11 and TCP/IP connections have been closed.  The exit
 status of the remote program is returned as the exit status of ssh.

我看到命令已经退出，所以我想不是所有的X11和TCP / IP连接都有已关闭。我怎么能知道这些ssh正在等待什么，以便我可以修复我的召唤命令的C + +应用程序，以清除任何留下，保持ssh打开。

I see that the command has exited, so I imagine not all the X11 and TCP/IP connections have been closed. How can I figure out which of these ssh is waiting for so that I can fix my summon command's C++ application to clean up whatever is being left behind that keeps the ssh open.

我不知道为什么这种失败只发生一些时间，而不是每次调用？它似乎发生大约50％的时间。我的C ++应用程序可以触发这个？

I wonder why this failure only occurs some of the time and not on every invocation? It seems to occur approximately 50% of the time. What could my C++ application be leaving around to trigger this?

更多背景：服务器是一个守护进程，启动时，它分叉和父退出，让子运行。客户端使用以下命令召集：

More background: The server is a daemon, when launched, it forks and the parent exits, leaving the child running. The client summons by using:

popen("ssh -n -o ConnectTimeout=300 user@host \"sererApp argsHere\""
      " 2>&1 < /dev/null", "r")

推荐答案

使用 libssh 或 libssh2 c $ c> popen（3）从C只调用 ssh（1），它本身是另一个C程序。如果你想要我的个人经验，我会说 libssh2 - 我用它在一个C ++程序，它的工作原理。

Use libssh or libssh2, rather than calling popen(3) from C only to invoke ssh(1) which itself is another C program. If you want my personal experience, I'd say try libssh2 - I've used it in a C++ program and it works.

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