4.8. Getting Notification of Underlying Protocol State Changes

The application can receive notification of intermediate protocol signaling state changes for both H.323 and SIP. The events for this notification must be enabled; see Section 4.14, Enabling and Disabling Unsolicited Notification Events.

Once these events are enabled, when a protocol state change occurs, the application receives a GCEV_EXTENSION event. The EXTENSIONEVTBLK structure pointed to by the extevtdatap pointer within the GCEV_EXTENSION event will contain the following information:

• extID - IPEXTID_IPPROTOCOL_STATE
• parmblk - A GC_PARM_BLK containing protocol connection status with the following parameter set ID and one of the following parameter IDs:
  • IPSET_IPPROTOCOL_STATE - A parameter set specific to underlying protocol states.
    • IPPARM_SIGNALING_CONNECTED - The signaling for the call has been established with the remote endpoint. For example, in H.323, a CONNECT message was received by the caller or a CONNECTACK message was received by the callee.
    • IPPARM_SIGNALING_DISCONNECTED - The signaling for the call has been terminated with the remote endpoint. For example, in H.323, a RELEASE message was received by the terminator or a RELEASECOMPLETE message was received by peer.
    • IPPARM_CONTROL_CONNECTED - Media control signaling for the call has been established with the remote endpoint. For example, in H.323, an OpenLogicalChannel message (for the receive direction) or an OpenLogicalCahnnelAck message (for the transmit direction) was received.
    • IPPARM_CONTROL_DISCONNECTED - Media control signaling for the call has been terminated with the remote endpoint. For example, in H.323, an EndSession message was received.

    Note: The parameter value field in this GC_PARM_BLK in each case is unused (NULL).

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