Dialogic Global Call IP Benutzerhandbuch

      default:
         printf(" Received Unknown Error cause\n");
         break;
   }
}

The SIP INFO message (as specified in IETF RFC 2976) provides a means for transporting 
application-level, session-related control information along the SIP signaling path after the setup of 
a SIP-controlled session has begun. INFO messages can be sent on an early INVITE-initiated SIP 
dialog (after a 101-199 provisional response) or on a confirmed dialog. The information of interest 
to the application can be contained in standard message header fields, proprietary header fields, or 
one or more MIME-encoded body parts. The Dialogic

®

 Global Call API library provides facilities 

for sending and receiving INFO requests and responses on a “pass-through” basis, meaning that 
there are no Global Call state changes associated with such messages. The library generates Call 
Info events to notify applications of incoming INFO messages, and Extension events for incoming 
INFO response messages. The 

 Send Message API is used for outgoing INFO 

requests and responses. 

Only one INFO request can be pending on a dialog. Once an INVITE request has been sent, 
another one cannot be sent until a response has been received. 

The following topics discuss how applications can send, receive, and respond to INFO requests.

Application access to the header fields in INFO messages requires that the mask value 
IP_SIP_MSGINFO_ENABLE must be set into the sip_msginfo_mask field of the 
IP_VIRTBOARD configuration data structure before 

 is called. Additionally, INFO 

messages frequently utilize MIME message bodies, and the ability to access MIME data must be 
enabled by setting the IP_SIP_MIME_ENABLE mask value in the same sip_msginfo_mask.

To send an INFO message, the application begins by creating a GC_PARM_BLK that contains an 
element with the IPSET_MSG_SIP parameter set ID, the IPPARM_MSGTYPE parameter ID and 
the IP_MSGTYPE_SIP_INFO parameter value. The application adds elements for the desired 
header fields (any combination of standard and proprietary header fields) and one or more MIME 
body parts, if appropriate, to the parameter block. (The technique for setting the header fields to be 
sent is described in 

page 183, and the technique for constructing MIME-encoded body parts is described in 

, on page 188.)  After constructing 

the complete parameter block, the application uses the 

 function to send the 

message. Because INFO messages relate to dialogs that have been initiated or confirmed, the