HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Working with Call-legs (Dialogs) 45
Call-leg API
that will be placed in the top Via header of the Request message. If the local
address is not set, the call-leg uses a default local address taken from the
SIP Stack configuration.
State
Indicates the state of the session setup between two SIP UAs. You can only
access the state parameter with a Get function and it is not modifiable.
Direction
Indicates whether the call-leg represents the incoming or outgoing side of the
session. You can only access the direction parameter with a Get function and it
is not modifiable.
Outbound Message
The outbound message is a handle to a message that the call-leg will use for the
next outgoing message. Before calling an API function that causes a message to
be sent, the application can get the outbound message and add headers and a
body. (Note that at this stage, the message is empty.) You cannot use the
outbound message to set headers that are part of the call-leg or transaction key,
such as To, From, Call-ID and Via headers. Such headers will be overwritten by
the SIP Stack.
Received Message
The last message (Request or Response) that was received by the call-leg. You
can get this message only in the context of the call-leg state-changed callback
function when the new state indicates that a call-leg transaction received a new
message. For example, when the call-leg enters the OFFERING state you can
get the incoming Invite Request message.
This parameter cannot be used for requests that the SIP Stack answers
automatically, such as CANCEL.
Call-leg Transaction Timers and Retransmission Count
The SIP Stack configuration determines the value of the timers and
retransmission count for all the SIP Stack transactions. The application can use a
set function to change the different timer values of the call-leg transactions. The
application can also control the number of retransmissions that the transactions
perform.