@VisibleForTesting
  public boolean hasResidualReaderThread() {
    return hasResidualReaderThread;
  }
A shared sender connection will leave a reader thread around to ensure that the
socket is properly closed at this end. When that is the case isResidualReaderThread
will return true.
geode-core/src/main/java/org/apache/geode/internal/tcp/Connection.java