[Asterisk-Users] Setting up asterisk for one user in private ipNAT.

[Rich Adamson]

To help clearify for those that don't have a good understanding of the
tcp-ip protocol, consider this:
- sip and rtp use the udp protocol (not tcp)
- all sip boxes (regardless of whether the box is a phone or *) _listen_
  on udp port 5060. (What udp port is used as the _source_ port when
  sending call setup data to the _destination_ port of 5060 is
  irrelavent. It can be any udp port.)
- * and _all_ phones (regardless of soft or hard) communicate the call
  setup info across udp port 5060.
- you can have 100's of phones and multiple asterisk boxes all using
  udp port 5060 as the protocol stack will keep track of each ip address
  and port number. No conflicts whatsoever.
- * and all sip phones will negotiate an rtp port over the sip 5060
  channel. * might pick udp port 12345 while the phone might pick
  udp port 23456. Once both ends have negotiated the rtp ports, audio
  is transported across those ports only (not the udp 5060 control port).

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> Hmm... For outgoing connections (from the softphone) that's true, but if you
> want asterisk to send a call to the softphone the default would be to send
> it to port 5060 (which is already taken by asterisk). If the softphone is
> setup to register to asterisk on another port, there should be no problem.
> 
> At least this is how I thought it worked ...
> 
> > -----Original Message-----
> > that isn't quite how ports work.. True, asterisk listens for 
> > udp connections on 5060. But the softphone won't make its 
> > outgoing connection on 5060. The OS will automatically choose 
> > an unused port number for the outgoing connection. So (for 
> > example) you might have the softphone talking on port 23107 
> > to asterisk on 5060, and asterisk on 5060 talking back to the 
> > softphone on 23107. No port conflict.
> > 
> > Now one place where you could have conflict is if asterisk is 
> > trying to use your soundcard for its console. Then the 
> > softphone client may have trouble getting the soundcard port opened.