TipcMsgGetSeqNum

Name

TipcMsgGetSeqNum — get the sequence number of a message

Synopsis

T_BOOL TipcMsgGetSeqNum(msg, seq_num_return) 
T_IPC_MSG msg; 
T_INT4 *seq_num_return; 

Arguments

msg — message to get sequence number from

seq_num_return — storage for sequence number

Return Values

TRUE if the sequence number was successfully retrieved from the message, FALSE otherwise.

Diagnostics

If TipcMsgGetSeqNum fails, it returns FALSE and sets the global SmartSockets error number to one of:

Description

TipcMsgGetSeqNum gets the sequence number of a message. The sequence number is used by GMD to detect duplicate messages. When a message with a delivery mode of T_IPC_DELIVERY_SOME or T_IPC_DELIVERY_ALL is sent through a connection, TipcConnMsgSend increments an internal per-connection sequence number and sets the sequence number of the message to the incremented value. If the message is later resent because of a GMD failure, TipcConnGmdMsgResend preserves the sequence number, which allows the receiving processes to detect the duplicate sequence number and thus avoid processing the same message twice.

Caution

If TipcMsgGetSeqNum returns FALSE, it does not store a value in seq_num_return.

See Also

TipcConnMsgSend, TipcConnGmdMsgResend

Examples

This example prints the sequence number of a message:

void T_ENTRY print_seq_num(msg) 
T_IPC_MSG msg; 
{ 
  T_INT4 seq_num; 
  if (!TipcMsgGetSeqNum(msg, &seq_num)) { 
    return;  /* error */ 
  }  
  TutOut("The message sequence number is %d.\n", seq_num); 
} /* print_seq_num */