[OpenSIPS-Users] Why does NAT keepalive only work for UDP?

[Klaus Darilion]

Bogdan-Andrei Iancu wrote:
> Klaus Darilion wrote:
>> Dan Pascu schrieb:
>>  
>>> Man, you have a lot of questions today... :P
>>>
>>> On Wednesday 12 November 2008, Iñaki Baz Castillo wrote:
>>>    
>>>> Hi, I wonder why SIP keepalive method (sending a NOTIFY/OPTIONS
>>>> perdiodically) just works for UDP, this is: why the request is not sent
>>>> via TCP?
>>>>       
>>> Mainly I guess it's because nobody did implement it, as none had a 
>>> need for it yet? Add to that that the TCP stack is handled 
>>> differently (inside opensips) and it's a complex beast which is not 
>>> easy to tap into as it is with UDP. Also, I guess historical reasons 
>>> was also a factor as it was meant as an improved replacement for the 
>>> (UDP only) solutions in the nathelper and mediaproxy modules (which 
>>> it is). While being improved it doesn't imply it has to be perfect, 
>>> so if you need TCP support, you are wellcome to implement it and 
>>> share it with us ;)
>>>     
>>
>> and make it non-blocking ;-)
>>   
> 
> Well, this is not difficult to do :) - because you do TCP connection 
> re-usage and avoid opening and searching for TCP conns.

I thought also TCP sending is synchronous.

regards
klaus

> 
> I think the question is not from technical point of view, but more a 
> logical one. Like known issues not to do TCP ping; does TCP ping may 
> help after all? how TCP ping and TCP keepalive work?
> 
> Regards,
> Bogdan