checkTransaction function

bool checkTransaction(TransactionBag _transactions, IncomingRequest request)

INVITE: true if retransmission false request

ACK: true ACK to non2xx response false ACK must be passed to TU (accepted state) ACK to 2xx response

CANCEL: true no matching invite transaction false matching invite transaction and no final response sent

OTHER: true retransmission false request

Implementation

bool checkTransaction(TransactionBag _transactions, IncomingRequest request) {
  switch (request.method) {
    case SipMethod.INVITE:
      InviteServerTransaction? tr = _transactions.getTransaction(
          InviteServerTransaction, request.via_branch!);
      if (tr != null) {
        switch (tr.state) {
          case TransactionState.PROCEEDING:
            tr.transport!.send(tr.last_response);
            break;

          // RFC 6026 7.1 Invite retransmission.
          // Received while in TransactionState.ACCEPTED state. Absorb it.
          case TransactionState.ACCEPTED:
            break;
          default:
            break;
        }

        return true;
      }
      break;
    case SipMethod.ACK:
      InviteServerTransaction? tr = _transactions.getTransaction(
          InviteServerTransaction, request.via_branch!);

      // RFC 6026 7.1.
      if (tr != null) {
        if (tr.state == TransactionState.ACCEPTED) {
          return false;
        } else if (tr.state == TransactionState.COMPLETED) {
          tr.state = TransactionState.CONFIRMED;
          tr.I = setTimeout(() {
            tr.timer_I();
          }, Timers.TIMER_I);

          return true;
        }
      }
      // ACK to 2XX Response.
      else {
        return false;
      }
      break;
    case SipMethod.CANCEL:
      InviteServerTransaction? tr = _transactions.getTransaction(
          InviteServerTransaction, request.via_branch!);
      if (tr != null) {
        request.reply_sl(200);
        if (tr.state == TransactionState.PROCEEDING) {
          return false;
        } else {
          return true;
        }
      } else {
        request.reply_sl(481);
        return true;
      }
    default:
      // Non-INVITE Server Transaction RFC 3261 17.2.2.
      NonInviteServerTransaction? tr = _transactions.getTransaction(
          NonInviteServerTransaction, request.via_branch!);
      if (tr != null) {
        switch (tr.state) {
          case TransactionState.TRYING:
            break;
          case TransactionState.PROCEEDING:
          case TransactionState.COMPLETED:
            tr.transport!.send(tr.last_response);
            break;
          default:
            break;
        }

        return true;
      }
      break;
  }
  return false;
}