Hi all, Continuing my work after I got good advice to my previous question (thanks quester), I've noticed a weird behavior I don't know how to explain. It doesn't bother me, but I'd like to understand it.

Short description: I am running a script on some HostA and this script resets HostB which I can control via ssh. To resume my interaction s with HostB I wanted to know when is HostB back online again. I followed the advice from quester and in a loop I try to connect to port 22 and read whatever the server listening there is about to say to me. Under normal circumstances, that server is the sshd and I should be reading a line beginning with "SSH". If this does not happen I go to sleep for 3 seconds and try again. I do this until I get my "SSH" line and then I go on with the rest of the script.

The thing is, the reboot procedure does take a while and in my try_to_connect-sleep loop I increment a counter just to see how many times I tried and just get some feedback that my script is still alive and probing the other host. the loop looks like this: 

do
    {
        $connected = connect(SOCK, $paddr);
        
        if($connected)
        {
            $line = <SOCK>;
            print("$line online\n");
            close(SOCK);
            $connected = 0;
            
            if ($line =~ /SSH/)
            {# connected to sshd - I'm ready 
                $done = 1;
            }
            else
            {# connected to ... who the heck is listening on port 22?
             ...some code here
            }          
        }
        else
        {
            $attempts++;
            print("Trying again ... ($attempts) \n");
            sleep(3); #sleep 3 seconds before trying again
        }
    }
    while(!$done);

[download]
My curiosity was triggered by how the "trying again" messages are printed. First one comes as expected, then then second one comes after 2-4 seconds. The third one can take 10 or more seconds to show up and then they come at 3 sec intervals. I am not bothered by how long it takes to get access to sshd so the fact that the total is around 30-40 seconds is not an issue. I am just curious about this weird timing and why is it always the second iteration?

Any ideas anyone?

Thanks!

In reply to Socket connect curiosity by RaduH

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