CODEWITHSUNDEEP
iphoneios4ios
Darshan Prajapati
Darshan Prajapati

Reputation: 843

Keeping SIP registration alive for interval less than 600 seconds in iPhone VOIP app

I am implementing a VOIP application in which I work with SIP protocol. As per SIP I need to refresh my registration with SIP server at certain interval. But when my app goes in background, my keepalive handler is invoked only after 600 seconds as per documents os Apple. But this is not desired with SIP protocol. To be able to keep my connection alive with server and receive incoming call, I need to send registration message before 600 seconds even when app is in background. According to Apple documentation this is not possible but stilll I have seen apps on AppStore which runs in background and keeps their registration on with SIP server even when registration interval is 60 seconds. They keep app running in background throughout. So how is this possible? I know that playing silent audio in background will survive but then AppReview process will reject it. But if its so, how Apple allowed other such apps on AppStore? Is there some standard way to achieve what I have described above? Any help is appreciated.

Upvotes: 3

Views: 6316

Answers (1)

alinoz
alinoz

Reputation: 2822

You don't have to send the registration more often. You can do something like this: configure your server to send keep alive packages to your sip client in order to keep the TCP connection open. Your server should support TCP connection and your client should communicate over TCP since apple is very restrictive in background mode and only the TCP connection is allowed to remain open in the background (if your TCP socket is wrapped with CFReadStreamRef).

The problem is no the registration message, this can be configured by the client by specifying the time between the connection attempts, and the sip sever will be fine with an interval of one hour between 2 registration messages. The real problem is how will the server contact the sip client in case of an incoming call or IM. Most of the sip clients will not have a public IP adress but most probably they will be behind a NAT. So there is no way the sip server can open a direct connection to the sip client, for this reason you have to keep a socket open between your client and the server.

None of the app in the appstore is sending registration message more often than 600s.

Do you use your own library for sip or you use pjsip? If you use pjsip i can give you more hints. What SIP server do you plan to use?

Some hints:

  • make sure you set in your app-info.plist the required background modes to "App provides Voice over IP services" and "App plays audio"

  • in case your app will not be tied to your own sip server then provide a way for the user to disable the allow_contact_rewrite pjsip param (usually u want this to be enable for bypassing the nat problem) since some session border controllers are not happy about this feature

  • make sure, in case you capture the messages send form the sip thread in your main thread, you are using a method to post them in the main thread

  • here are described some other interesting issues

  • have a lot of coffee prepared :))

Upvotes: 4

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