UCT IMS Client Source Code Analysis

UCT IMS Client Source Code Analysis

Overview

It is an IMS user agent based on osip/eXsip library.  The source code the document analyzes is uctimsclient1.0.6

•         Feature list:

–     AKAv1 and AKAv2 registration

–     Subscribe to reg event and watcher info event

–     instant messaging

–     DTMF tones via SIP INFO messages

–     Presence support

–     XCAP Presence Rules Support

•         Depends on following open source lib:

–     libosip2

–     libeXosip2

–     Gstreamer libraries

–     libgtk2

•         File List

–     Entry

•         imsUA.c: application entry, create GUI, init eXosip2 library and fetch events from eXosip2 library

–     GUI

•         Interface.c: used to create GUI and set GUI signal handler

•         Callback.c: GUI signal handlers

•         Ims_interface_event_handler.c: functions called by signal handlers in callback.c

•         Common_interface_event_handler.c: functions called by event handlers in callback.c

•         Preferences.c: used to set preference parameters

•         Presence.c: edit and show presence info

•         Watchers.c: list who are interested in your presence info

•         Xcap.c: handler XDMS manager

–     eXosip event

•         Ims_exosip_event_handler.c: callback called by eXosip2 library

•         Common_exosip_event_handler.c: common functions called by callbacks in Ims_exosip_event_handler.c

•         Media.c: common functions called by callbacks in Ims_exosip_event_handler.c

–     authentication

•         DigestAKAv1MD5.c

•         Base64.c

•         Md5.c

•         Rfc2617.c

–     media:

•         Gstreamer.c: used to set GStreamer pipeline for audio and video call

–     Utilities:

•         Support.c: utilities for GUI fuctions

•         Useful_method.c: utilities for processing SIP message

•         Sdp_method.c: used to build SDP parameters for SIP message

–     SIP-to-IMS Gateway(not used)

•         Milenage.c

•         Rijndael.c

•         Sound_conv.c

 

startup process

create_imsUA: create GUI, and set signal handler for each GUI component

initialise_eXosip

set eXosip event process function get_exosip_events: all events from eXosip is fetched by this function, and then handle in Ims_exosip_event_handler.c

 

 

Registration Process

User click “Registration”:

on_register2_activate --->ims_send_register:

Build and send a register request(eXosip_register_send_register)

 

Wait for event EXOSIP_REGISTRATION_FAILURE:

If error code is 401, it does not mean registration failed, it means we need to do authentication:

ims_process_401: build an another register request with authentication info, and send it.

 

wait for event EXOSIP_REGISTRATION_SUCCESS:

ims_process_registration_200ok:

subscribe presence info and watchers info

Presence and watcher

When any buddy is online or update its presence info, or anyone subscribes your presence info, the event EXOSIP_SUBSCRIPTION_NOTIFY will be received:

ims_process_notify:

presence_process_notify to handle presence info, or watchers_process_notify to handle watch info

Calling Process

User click “Call or answer”button:

on_call_button_clicked---ims_call_initiate--ims_call_initiate

build and send a invite request(eXosip_call_send_initial_invite)

 

wait for event EXOSIP_CALL_RINGING:

ims_process_18x:

(the status code is 183 on the first round)

if require 180rel: build and send a prack(eXosip_call_send_prack)

 

wait fro event EXOSIP_CALL_MESSAGE_ANSWERED:

ims_process_2xx:

build and send update message: eXosip_call_build_update and eXosip_call_send_request

 

wait for message EXOSIP_CALL_RINGING:

ims_process_18x:

(the status code is 180 on the second round)

initialiseRingingPipeline: initialize GStreamer ringing pipeline.

 

wait until remote accept or reject the call:

EXOSIP_CALL_ANSWERED means accept call:

ims_process_200ok:

build and send an ack message.

start_rtp_session: destroy GStreamer ringing pipeline, and start GStreamer voice and video pipeline

 

Incoming Call:

event EXOSIP_CALL_INVITE:

ims_process_incoming_invite

if busy at this moment, send reject(eXosip_call_send_answer(je->tid, 486, NULL))

build and send answer: (eXosip_call_send_answer(je->tid, 183, session_progress))

 

wait EXOSIP_CALL_MESSAGE_NEW:

ims_process_prack: (why there is no place to send an ack for prack?)

build and send answer(eXosip_call_send_answer)

initialiseRingingPipeline: initialize GStreamer ringing pipeline.

 

if user click “call or answer” button:

on_call_button_clicked---- ims_call_answer

build and send answer(eXosip_call_send_answer)

 

wait for event EXOSIP_CALL_ACK:

ims_process_ack:

start_rtp_session: destroy GStreamer ringing pipeline, and start GStreamer voice and video pipeline

 

 

If user click “hangup or refuse” button:

on_hangup_button_clicked--- terminate_call

 

DTMF:

click “DTMF digits” buttons during call:

common_send_dtmf:

create and send request: eXosip_call_build_info and eXosip_call_send_request

 

IM

user click “start chat” button:

on_start_chat_clicked--ims_open_im_window:

if no IM window, create_im_window: connect signal

  g_signal_connect ((gpointer) send_im_button, "clicked",

                    G_CALLBACK (on_send_im_button_clicked),

                    NULL);

 

the peer who receives IM message:

receives event EXOSIP_MESSAGE_NEW:

ims_start_im_session:

if no IM window, create_im_window: connect signal

  g_signal_connect ((gpointer) send_im_button, "clicked",

                    G_CALLBACK (on_send_im_button_clicked),

                    NULL);

 

on_send_im_button_clicked:

ims_send_instant_message: build and send message(eXosip_message_send_request)