Connection refused when trying connecting to postgresql

Question

#Edit Sorry its not connect to PostgreSQL but im trying to connect to materialized shell but it's getting an error like below

 psql: could not connect to server: Connection refused
    Is the server running on host "localhost" (::1) and accepting
    TCP/IP connections on port 6875?
could not connect to server: Connection refused
    Is the server running on host "localhost" (127.0.0.1) and accepting
    TCP/IP connections on port 6875? 

how can i solve this?

Thanks.