public static byte[] getMembershipId(ClientProxyMembershipID client) {
    try {
      HeapDataOutputStream hdos = new HeapDataOutputStream(256, client.getClientVersion());
      ((InternalDistributedMember) client.getDistributedMember()).writeEssentialData(hdos);
      return hdos.toByteArray();
    } catch (IOException ioe) {
      throw new InternalGemFireException(
          "Unable to serialize identity",
          ioe);
    }
  }
Convert a ClientProxyMembershipID distributed member ID array into one usable by EventIDs

@param client the client's ID
@return a byte array that may be used in EventID formation
geode-core/src/main/java/org/apache/geode/internal/cache/EventID.java