pqxx: broken_connection on trying to connect to posgres db - postgresql

Question

I have this problem trying to connect to the local postrgres databases. Until now i succeeded to connect to the same databases using jdbc or working directly in PGAdmin, this error happens when i try to connect using pqxx library or from shell:
pqxx code:
#include <pqxx/connection.hxx>
int main(){
pqxx::connection conn("user=postgres port=5432 dbname=pqxx-test password=postgres");
return 0;
}
or from shell, as user postgres:
psql pqxx-test
both the cases raise this error:
could not connect to server: No such file or directory Is the server
running locally and accepting connections on Unix domain socket
"/var/run/postgresql/.s.PGSQL.5432"
Searching for the solution i think i understood i have to edit pq_hba.conf and postgresql.conf files in order to connect in these ways, but in pg_hba.conf is already set:
local all all md5
and in postgresql.conf
listen_addresses='*'
And by the way, i'm not even able to edit these files because of a problem with the viminfo, but maybe this is another problem..
Can anyone help me?
edit:
using PostgreSQL 9.6.2
on Ubuntu 14.04
edit:
as postgres user, if i ask for the postgre version using:
psql -V
the result is 9.6.2
but looking at the file system hierarchy, all conf file are inside this folder
/opt/PostreSQL/9.4/data/
can that be the problem?

Answer 1

You seem to have a mix of client-side postgresql 9.6 configured for the ubuntu FS layout and a postgresql server 9.4 presumably downloaded from EntrepriseDB (and installed under /opt/PostgreSQL) using its own layout.
Assuming that the postgresql is running, the simplest solution is to add host=localhost to your connection string, so that it will use a TCP connection instead of the Unix domain socket /var/run/postgresql/.s.PGSQL.5432 that does not exist because of the mismatch.