LDAPException(resultCode=91 (connect error)， errorMessage='试图连接服务器时发生错误

I am tring to make an android app to connect at an LDAP server. I am using UnboundId library so my app to be able to establish an LDAP connection. The problem is the resultCode 91-connection error and I don't know how to resolve it. The LDAP server is up and running because my desktop app can establish a connection. I will attach the code:I am tring to make an android app to connect at