1. NEXTSP nextsp;
  2. nextsp.begin(isServer,"43750697",&onCallback);
  3. nextsp.send("test");
  4. nextsp.update();

  #include <nExtSP.h>

  NEXTSP nextsp;
  
  void onCallback(byte* b,int length){
  //...
  }
  
  void setup(){
  //            boolean, if esp32 is server or client
  //              |      choose a unique id for every pair
  //              |         |        register callback function
  //              v         v            v
  //...
  nextsp.begin(isServer,"43750697",&onCallback);
  //...
  }
  
  void loop(){
  //...
  nextsp.send("test");
  //...
  nextsp.update(); // call once every loop.
  //...
  }