Communication with tcp-ip

Hello,

I must communicate with scale over TCP-IP to recover the weight.

The DB is Oracle Database 12c Standard Edition Release 12.1.0.2.0 - 64bit Production.

I use package UTL_TCP.

My communication is working, sometimes, the communication is pending.

It's working 10 or 15 times, I wait 30 minutes after the communication is pending.

I check the session I see this is Always the same  query,

BEGIN

   :1 := DBMS_NETWORK_ACL_ADMIN.get_host_aclids (:2, );

END;

Have you an idea for the solution ?

Thanks.