code: public void setPduProcessorDegree(int pduProcessorDegree) throws IllegalStateException {
          if (!getSessionState().equals(SessionState.CLOSED)) {
              throw new IllegalStateException(
                      "Cannot set PDU processor degree since the PDU dispatcher thread already created");
          }
          this.pduProcessorDegree = pduProcessorDegree;
      }
docs: Set total thread can read PDU and process it in parallel. It's defaulted to
  3.
  
  @param pduProcessorDegree is the total thread can handle read and process
  PDU in parallel.
  @throws IllegalStateException if the PDU Reader has been started.