Version 2 (modified by bennylp, 15 years ago) (diff)


Symbian Access Point Reconnection

Table of Contents

  1. Problem description
  2. Issues
    1. Restart everything
    2. Selective update
  3. Scenarios
    1. Access point disconnection

This article describes some issues and their corresponding solutions related to access point disconnection, reconnection, and change in your Symbian PJSIP applications.

Problem description

Access point disconnection and reconnection are scenarios that need to be handled in mobile applications. Few issues or scenarios related to this for example are:

  • user moves outside the range of a Wi-Fi access point (AP) and lost the connection
  • user moves outside the range of one AP and reconnect to another
  • the handset may get new IP address if user reconnects to different AP

Each of the scenarios above may need different handling in the application.


When the connection is reconnected, the handset may get different IP address than what it previously got. There are few ramifications of this, for example if PJSUA-LIB is used:

  • the SIP registration needs to be updated with a new Contact URI
  • the account URI also needs to be updated
  • media addresses need to be updated
  • if there is ongoing dialog, the remote party needs to be informed with new Contact URI as well as new media (RTP/RTCP) addresses.

Note that at this time of writing (2009/02/25, PJSIP v1.1), PJSIP does not have the capability to monitor the status of the underlying IP connection used by the application, so the application must implement the detection itself (for example using connection progress monitor in Symbian). Having said that, PJSIP does have some capability to detect some IP address change scenarios, for example by monitoring the IP address in SIP REGISTER response or in STUN Binding response when ICE transport is used and STUN is enabled.

Once the application has detected that the IP interface address has changed, there are two solutions to inform PJSIP about this.

Restart everything

The most straightforward solution is of course to restart everything, which means in pjsua terms to call pjsua_destroy() and followed by pjsua_create(), pjsua_init(), and so on. While this solution may sound crude, it is the easiest to do and as will be explained later it is not considerably worse then the more refined alternative.

Selective update

Alternatively there may be a way to allow the stack to continue to run, updating the address information when necessary. This approach will require some specific features to be used, as well as some actions by the application when it detects that the IP address has changed.

The specific configuration and tasks will be explained below.


Access point disconnection