 
 void ZCommand::reSendLastPacket(WiFiClientNode *conn)
 {
+  if(conn == NULL)
+  {
+    Serial.print("[ 0 0 0 ]");
+    Serial.print(EOLN);
+  }
+  else
   if(conn->lastPacketLen == 0) // never used, or empty
   {
     Serial.printf("[ %d %d %d ]",conn->id,conn->lastPacketLen,0);

    currentExpiresTimeMs = millis() + 1000;
  if(!crReceived)
    return;
  delay(200); // give a pause after receiving command before responding
  // the delay doesn't affect xon/xoff because its the periodic transmitter that manages that.
  doSerialCommand();
}

  {
    XON=false;
    firstConn = conns;
    while(firstConn != NULL)
    {
      firstConn->lastPacketLen = 0;
      firstConn = firstConn->next;
