docs: protected boolean readMeta(@NotNull final WireIn wireIn) {
          final StringBuilder event = Wires.acquireStringBuilder();
  
          @NotNull ValueIn valueIn = wireIn.readEventName(event);
  
          if (csp.contentEquals(event)) {
              @Nullable final String csp = valueIn.text();
  
              long cid;
              event.setLength(0);
              valueIn = wireIn.readEventName(event);
  
              if (CoreFields.cid.contentEquals(event))
                  cid = valueIn.int64();
              else
                  throw new IllegalStateException("expecting 'cid' but eventName=" + event);
  
              event.setLength(0);
              valueIn = wireIn.readEventName(event);
  
              if (CoreFields.handler.contentEquals(event)) {
                  if (cidToHandle.containsKey(cid)) {
                      String registeredCsp = cidToHandle.get(cid).csp();
                      if (!csp.equals(registeredCsp))
                          Jvm.warn().on(getClass(), "cid: " + cid + " already has handler registered with different csp, registered csp:" + registeredCsp + ", received csp: " + csp);
                      // already has it registered
                      return false;
                  }
                  handler = valueIn.typedMarshallable();
                  handler.nc(nc());
                  handler.closeable(this);
  
                  try {
                      if (handler instanceof Registerable) {
                          Registerable registerable = (Registerable) this.handler;
                          registry.put(registerable.registryKey(), this.handler);
                          registerable.registry(registry);
                      }
  
                  } catch (Exception e) {
                      Jvm.warn().on(getClass(), e);
                  }
  
                  if (handler instanceof ConnectionListener)
                      nc().addConnectionListener((ConnectionListener) handler);
  
                  if (handler() instanceof HeartbeatEventHandler) {
                      assert heartbeatEventHandler == null : "its assumed that you will only have a " +
                              "single heartbeatReceiver per connection";
                      heartbeatEventHandler = (HeartbeatEventHandler) handler();
                  }
  
                  handler.cid(cid);
                  handler.csp(csp);
                  lastCid = cid;
                  cidToHandle.put(cid, handler);
  
                  if (handler instanceof WritableSubHandler)
                      writers.add(((WritableSubHandler) handler).writer());
              } else
                  throw new IllegalStateException("expecting 'cid' but eventName=" + event);
              return true;
          } else if (CoreFields.cid.contentEquals(event)) {
              final long cid = valueIn.int64();
              if (cid == lastCid)
                  return false;
              lastCid = cid;
              handler = cidToHandle.get(cid);
  
              if (handler == null) {
                  throw new IllegalStateException("handler not found : for CID=" + cid + ", " +
                          "known cids=" + cidToHandle.keySet());
              }
          } else {
              throw new IllegalStateException("expecting either csp or cid, event=" + event);
          }
  
          return false;
      }