PostgresSQL server connectiong problem with C-language...

Hi,

I wrote a C-program for connecting to postgresSQL server and get the
data from the database.

The program is as fallows:-
Code: ( c )

#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h" /* libpq header file */
int
main()
{
char state_code[3];
char query_string[256]; /* holds
constructed SQL query */
PGconn *conn; /* holds
database connection */
PGresult *res;
int i;
conn = PQconnectdb("dbname=test"); /*
connect to the database */
if (PQstatus(conn) == CONNECTION_BAD) /* did
the database connection fail? */
{
fprintf(stderr, "Connection to database failed.\n");
fprintf(stderr, "%s", PQerrorMessage(conn));
exit(1);
}
printf("Enter a state code: "); /*
prompt user for a state code */
scanf("%2s", state_code);
sprintf(query_string, /*
create an SQL query string */
"SELECT name \
FROM statename \
WHERE code = '%s'", state_code);
res = PQexec(conn, query_string); /* send
the query */
if (PQresultStatus(res) != PGRES_TUPLES_OK) /* did
the query fail? */
{
fprintf(stderr, "SELECT query failed.\n");
PQclear(res);
PQfinish(conn);
exit(1);
}
for (i = 0; i < PQntuples(res); i++) /* loop
through all rows returned */
printf("%s\n", PQgetvalue(res, i, 0)); /*
print the value returned */
PQclear(res); /* free result */
PQfinish(conn); /*
disconnect from the database */
return 0;
}

I changed the postgresql.conf and pg_hba.conf files.

listen_addresses = '*' # what IP address(es) to listen on;
# comma-separated list of addresses;
# defaults to 'localhost', '*' = all
# (change requires restart)
port = 5432 # (change requires restart)
max_connections = 100
----------------------------------------------------------------------------

# TYPE DATABASE USER CIDR-ADDRESS METHOD
local all all trust

# The same using local loopback TCP/IP connections.
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
host all all 0.0.0.0/0 trust

every time I a getting the same error when I was trying to run the program:-

Connection to database failed.
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"?

Thanks for reading this long mail.
could any one plz help me how to solve this problem...

Thanks & Regards...
Madhu.