• You have specified no host so it assumes localhost.
• You have specified no port, so it assumes 389.
• You have specified no bind DN so it assumes anonymous bind.
• You have specified no filter so it assumes objectclass=* (I think).

Any of those being bad assumptions could cause it to fail. Generally this should return at least the RootDSE of the local LDAP instance on 389.

It worked after specifying the base DN of my Server. My LDAP Server has multiple schemas. So need to specify the Base DN from where it has to check from.