The important API calls are documented below. More thorough documentation is being written, but this should provide all of the necessary information to construct a working SR-RTP application. Many of these function calls have a complementary function that should be called when the Congestion Manager is enabled.

API calls

Initialization Functions

• rtp_channel_t srrtp_create_channel()
  rtp_channel_t srrtp_create_cm_channel(int cm_socktype, int cm_congctlalg)

  srrtp_create_channel creates an SR-RTP communications channel. This is the API call that initializes the channel. For use with the Congestion Manager (CM), srrtp_create_cm_channel provides a means of opening an SR-RTP channel where cm_socktype specifies the type of CM socket to use (i.e., buffered, rate-controlled, or ALF).
  
  

• int srrtp_open(rtp_channel_t ch, u_int32_t saddr, u_short sport, u_short scport, int *rtpsock, int *rtcpsock)
  int srrtp_cm_open(rtp_channel_t ch, u_int32_t saddr, u_short sport, u_short scport, int *rtpsock, int *rtcpsock)

  srrtp_open initializes a connection to a listening SR-RTP socket.

  Parameters:

  • ch: instance of the SR-RTP channel
  • saddr: INET address of the machine to connect to
  • sport: port on the machine that is listening. The control (RTCP) port will be automatically set to one higher than this number.
  • rtpsock: returns the file descriptor of the data socket
  • rtcpsock: returns the file descriptor of the control socket
  
  
  
• int srrtp_listen(rtp_channel_t ch, u_short rport, u_short rcport, int *rtpsock, int *rtcpsock)
  int srrtp_cm_listen(rtp_channel_t ch, u_short rport, u_short rcport, int *rtpsock, int *rtcpsock)

  srrtp_open initializes an SR-RTP socket to listen for incoming connections.

  Parameters:

  • ch: instance of the SR-RTP channel
  • rport: port on which to listen for data
  • rcport: port on which to listen for control data
  • rtpsock: returns the file descriptor of the data socket
  • rtcpsock: returns the file descriptor of the control socket
  
  
  

Data Path Functions

• void srrtp_read(rtp_channel_t ch, int seqno, char *data, int *len, u_int32_t *fromaddr, u_int16_t *fromport)
  void srrtp_read_and_cancel(rtp_channel_t ch, int seqno, char *data, int *len, u_int32_t *fromaddr, u_int16_t *fromport)

  This function is called by the application in order to read an ADU from the reassembly buffers into

  Parameters:

  • ch: instance of the SR-RTP channel
  • seqno: ADU sequence number (monotonically increasing)
  • data: buffer to hold received data
  • len: reported length of received data
  • fromaddr: reported origin address
  • fromport: reported origin port
  
  
  
• void srrtp_send(rtp_channel_t ch, char *adu, int len, u_int8_t more, u_int16_t priority)
  

  This function sends an ADU on the SR-RTP data channel. All packet fragmentation, etc., is performed invisibly to the application.

  Parameters:

  • ch: instance of the SR-RTP channel
  • adu: buffer holding ADU to be sent
  • len: length of buffer
  • more: are there more ADUs to send?
  • priority: priority field (set MSB if retransmit is necessary)
  
  
  
• void srrtp_app_notify(rtp_channel_t ch, int seqno, int len, int layer)
  

  An SR-RTP application must implement this callback. The SR-RTP layer makes this callback when a complete ADU arrives. The application is notified when this event occurs, and responds appropriately, usually by calling srrtp_read.
  
  

• void srrtp_app_send(rtp_channel_t ch)
  

  This is used with the CM if a send callback is made from the CM. It is a way for the application to send ADUs via callback mechanisms.