Implemented empty state_string function
diff --git a/OpenSSL/SSL.py b/OpenSSL/SSL.py
index f8f5e02..190e4ac 100644
--- a/OpenSSL/SSL.py
+++ b/OpenSSL/SSL.py
@@ -1592,6 +1592,7 @@
 
         :return: A string representing the state
         """
+        return _ffi.string(_lib.SSL_state_string_long(self._ssl))
 
     def server_random(self):
         """