code: public byte[] sendEnquireLinkResp(OutputStream os, int sequenceNumber)
              throws IOException {
          synchronized (os) {
              return pduSender.sendEnquireLinkResp(os, sequenceNumber);
          }
      }
docs: /*
  (non-Javadoc)
  
  @see org.jsmpp.PDUSender#sendEnquireLinkResp(java.io.OutputStream, int)