Using dblink in Postgres

select contractid from tcim_s_enterprice
EXCEPT
select contractid from
dblink (
        'host=172.16.51.25 port=5432 dbname=contract user=eshop password=iTLxUQ7FUv1sBu',
        'select contractid from tcrm_s_contractmaster '
    ) AS B (
        contractid CHARACTER VARYING (100)
    )