SIP Thought Experiment

This is not really a problem per se, but a minor niggle that cropped up that will probably never be a real-world issue, but someone may be able to help me understand better.

I have a cellphone plan with 100 minutes, so I set up CSipSimple on my Android phone with my VoIPo SIP credentials so I can make calls if I ever exceed this 100 minutes. It works fine, and test calls are placed without issue.

The niggle is that, if I am connected to VoIPo via SIP but attempt to place a normal cellular call to my home VoIPo number, the call is not completed and the home line does not ring. One of two things happens when I try: (i) the call just ends on my cellphone with the message "Call Ended", or (ii) the line rings on my cellphone and after a few seconds a female voice says "Please enter your password followed by the pound key". In either circumstance, the call is not completed and the home VoIPo line does not ring.

I had thought that with SIP in the mix it would just be added as another endpoint for an incoming call, so if someone tried to call while I was connected to SIP, the home line would ring and also the SIP client on my phone would ring. Is this not the case? Does SIP instead "take over" the line whilst it is connected? After the SIP client on my cellphone has been disconnected for a few minutes, the home VoIPo line becomes ringable again.

Just wondering if this is how it was meant to be and my rudimentary understanding was wrong, or what. As I say, it's not really a big problem, just something I was wondering about.

Maybe I don't understand your explanation. Let me repeat back what I think you're doing, and tell me if that sounds correct.

Your CsipSimple app is configured for your voipo account. Your home voip is configured for the SAME Voipo account. You're trying to call yourself from the same number; from your Csip to your house. But still.... you're trying to call the same number you're calling from. Does this sound about right? You didn't happen to purchase a 2nd VoipO account with a 2nd number; did you? If not, then you'll probably have a problem doing what you're trying to do. Imagine forwarding your home number TO your cell phone. Then, you take your cell phone and try to call your home phone. What do you think is going to happen? That's pretty much what's happening here. Your "VOIPO" line is already in use. (From your android CsipSimple app). Yet, you're trying to call your home voipo which is the same account. The best I would have hoped for in this scenario is that you went straight to voicemail. Which it sounds like you sort of have. As for an incoming call; yes, both the home and Csip can ring, but whichever answers first gets it. Not both. Please correct me if I misunderstood part of what you were saying.

Mostly correct.

I did find the solution was to include the port number in my SIP address on my cellphone, and now both phones (the cellphone through CSipSimple and the home VoIPo line) ring whenever someone else tries to call. I found that fix on these forums just earlier today.

I use this all the time with t-mobile $30 plan 100mins + unlimited data and text. but if you use your home wifi and the port for the ata is 5060 then this will happen because t-mobile you have to use port 5060, so if you use home wifi you need to set your ata to 5061 then it will always work, and not conflict with each other.