xinetd.d listening twice on port 69

[David Curry]

Paul Howarth wrote:

> Andy Green wrote:
>
>> David Curry wrote:
>> | Andy Green wrote:
>> |
>> |>
>> |> But I am still bemused by the two listening sockets on the same port
>> |> being possible.  Maybe it is some kind of cool load balancing 
>> feature I
>> |> never heard of.  Can anyone else here explain how it can be?
>> |>
>> |> - -Andy
>> |
>> |
>> |
>> | May be this is a dumb question from a clueless neophyte, but does the
>> | phenomenon constitute a security problem that needs to be addressed?
>>
>> Probably not, because I'm pretty sure it will only allow it if the two
>> listens are coming from inside the same process ID.
>>
>> For example in one window
>>
>> [root at server root]# nc -l -p 1234
>>
>> works and is listening
>>
>> [root at server root]# netstat -plutn | grep 1234
>> tcp        0      0 0.0.0.0:1234                0.0.0.0:*
>> ~    LISTEN      19055/nc
>>
>> If you try to start a second nc to the same port in another window...
>>
>> [root at server root]# nc -l -p 1234
>> Can't grab 0.0.0.0:1234 with bind
>>
>>
>> So it seems that maybe it's just a (little-known?) feature for a single
>> process rather than a bug?
>
>
> No, you've been setting up TCP sockets. If you do it with UDP sockets 
> (nc -l -u -p 1234) you can have multiple listeners, and they don't 
> have to be the same process or even started by the same user.
>
> Paul.
>
Thanks for the ed info, gentlemen.