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4.14.4 Receiving Responses to OPTIONS Requests
When the Dialogic
®
Global Call API library’s SIP stack receives a response to a SIP OPTIONS
request, it generates a GCEV_EXTENSION event of type IPEXTID_RECEIVEMSG.
The GC_PARM_BLK associated with the Extension event will contain a parameter element as
follows:
IPSET_MSG_SIP
IPPARM_MSGTYPE parameter ID
and one of the following values:
• IP_MSGTYPE_SIP_OPTIONS_OK
• IP_MSGTYPE_SIP_OPTIONS_FAILED
The application can also retrieve the specific SIP response code from the event’s parameter block
using the IPSET_MSG_SIP set ID and the IPPARM_MSG_SIP_RESPONSE_CODE parameter
ID.
In the case of an IP_MSGTYPE_SIP_OPTIONS_OK response, the application can use the
techniques described in Section 4.9.6, “Retrieving SIP Message Header Fields” to retrieve message
header fields of interest, including:
• Request-URI
• To header field
• From header field
• Contact URI
• Accept header field
• Accept-encoding header field
• Accept-language header field
• Supported header field
• Allow header field
• Require header field
• Call-ID header field
The application can also extract any MIME information from the message body using the
techniques described in Section 4.10.3, “Getting MIME Information”, on page 191. Note that
responses to OPTIONS requests are the single case where the MIME part containing SDP
information is exposed to the application rather than handled internally by the Dialogic
®
Global
Call API library. The SDP information is identified by the string “Content-Type: application/sdp”.
In the case of an IP_MSGTYPE_SIP_OPTIONS_FAILED response, the application can use the
techniques described in Section 4.9.6, “Retrieving SIP Message Header Fields” to retrieve the
following message header fields:
• Request-URI
• To header field
• From header field