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

Working with Transmitters 219

Transmitter State Machine

The RvSipTransmitterStateChangedEv() callback reports transmitter state

changes and state change reasons. The state change reason indicates the reason

for the new state of the transmitter. The transmitter associates with the

following states:

RVSIP_TRANSMITTER_STATE_UNDEFINED

Indicates that the transmitter was not yet initialized.

RVSIP_TRANSMITTER_STATE_IDLE

The initial state of the transmitter. Upon transmitter creation, the transmitter

assumes the IDLE state. It remains in this state until

RvSipTransmitterSendMessage() is called. The transmitter then moves to the

RESOLVING_ADDR state and starts the address resolution process.

RVSIP_TRANSMITTER_STATE_RESOLVING_ADDR

Indicates that the transmitter is about to start the address resolution process.

After RvSipTransmitterSendMessage() is called, the transmitter copies the

supplied message and moves to the RESOLVING_ADDR state. The transmitter

then uses RFC 3261 rules to get the remote URI from the message, and the

procedures of RFC 3263 to resolve the address by querying the DNS server.

When the DNS procedure is completed and the destination address is

determined, the transmitter moves to the FINAL_DEST_RESOLVED state.

RVSIP_TRANSMITTER_STATE_FINAL_DEST_RESOLVED

Indicates that the transmitter has completed the address resolution process and

that it has a destination address to use. The application can use the

RvSipTransmitterGetDestAddress() function to get the destination address. The

application can change the destination address using the

RvSipTransmitterSetDestAddress() function. If the application did not set the

Fix Via flag, the FINAL_DEST_RESOLVED state is the last chance for the

application to fix the Via by itself before the message is sent.

In this state, the application can hold the message sending activity by calling the

RvSipTransmitterHoldSending() function. If so, the transmitter will move to the

ON_HOLD state. Otherwise, the message will be sent when the state changed

callback returns.