The MY_TRANSPORT_MAX_TX_FAILURES seems to do the job perfectly, I adjusted it down to 1 for the node, and resend the message a couple of times if it fails.

Thank you for your support :)

Also thanks to berkseo, your code also works for me, but I do prefer the built in way now that I know of it. Less code for me to write and maintain :)

n my MySensors network I have a ESP8288 MQTT gateway and two repeaters and a number of sensor nodes. One of these are a button-node that I like to move around in my house. This means that sometimes I move it from one end of the house to the other, so it can no longer connect to the parent node it used to use. I know how to request an acknowledgement in the send method so I can resend the button-press-message, but is there a way to "give up" a parent node after a number of failed transmissions, and broadcast for a new one?
I know I can do this by pulling the battery and restarting the node, but I'd rather it just do it by itself

It's part of my code, ... roughly so

void check_parent() {
  _transportSM.findingParentNode = true;
  CORE_DEBUG(PSTR("MyS: SEND FIND PARENT REQUEST, WAIT RESPONSE\n"));
  tx_led ();
  _sendRoute(build(_msg, 255, NODE_SENSOR_ID, 3, 7).set(""));
  wait(2000, 3, 8);
  if (_msg.sensor == 255) {
    if (mGetCommand(_msg) == 3) {
      if (_msg.type == 8) {
        Ack_FP = 1;
        CORE_DEBUG(PSTR("MyS: PARENT RESPONSE FOUND\n"));
      }
    }
  }
  if (Ack_FP == 1) {
    CORE_DEBUG(PSTR("MyS: FIND PARENT PROCESS\n"));
    rx_led ();
    Ack_FP = 0;
    transportSwitchSM(stParent);
    flag_nogateway_mode = 0;
    flag_find_parent_process = 1;
    CORE_DEBUG(PSTR("MyS: STANDART TRANSPORT MODE IS RESTORED\n"));
  } else {
    bc_led ();
    _transportSM.findingParentNode = false;
    CORE_DEBUG(PSTR("MyS: PARENT RESPONSE NOT FOUND\n"));
    _transportSM.failedUplinkTransmissions = 0;
    fp_timer = millis();
  }
}

if ( !transportCheckUplink() ) {
   asm volatile ("  jmp 0"); // CRASH, BURN AND RESET
 }

It does the trick ... though it really bothers my developer-heart ;)

(254 is button node, 252 is repeater I turned off after the button node was started up)

64442 TSF:PNG:SEND,TO=252
64479 !TSF:MSG:SEND,254-254-252-252,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=NACK:1
66488 TSF:CKU:FAIL

But no looking for a new parent.

I tried calling some functions I thought sounded like they would help me, without really knowing. I guess it is not functions that a user like me really should use?:

if ( !transportCheckUplink() ) {
  stParentTransition();
  while ( isTransportSearchingParent() ) {
    stParentUpdate();
  }
}

This starts what appears to be a new parent search, but it never completes:

151171 TSF:MSG:SEND,254-254-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
153180 !TSM:FPAR:NO REPLY
153182 TSM:FPAR
153219 TSF:MSG:SEND,254-254-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
155228 !TSM:FPAR:NO REPLY
155230 TSM:FPAR
155267 TSF:MSG:SEND,254-254-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
157276 !TSM:FPAR:NO REPLY
157278 TSM:FPAR
157315 TSF:MSG:SEND,254-254-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
159324 !TSM:FPAR:FAIL
159326 TSM:FAIL:CNT=7
159328 TSM:FAIL:DIS
159330 TSF:TDI:TSL
161333 !TSM:FPAR:NO REPLY
161335 TSM:FPAR

At this point I have started my repeater again, and I think it should also find either the gateway or another node.