no pg_hba.conf entry for host

i have written a program:

#include<stdlib.h>
#include<libpq-fe.h>
int main()
{
PGconn *myconnection = PQconnectdb("host = indra user = surabi password = test123 port = 5432 dbname=bpsimple");
if(PQstatus(myconnection) == CONNECTION_OK)
printf("Connection made\n");
else
printf("Connection failed : %s\n", PQerrorMessage(myconnection));
PQfinish(myconnection);
return 0;
}

from one host 3.70.201.172 , I try to connect to a remote host "indra", that is running postgreSQL server.

I ran the postmaster on "indra" like:
/usr/local/pgsql/bin/postmaster -h 3.70.201.172 -i -D ./data/&

However i get this error message
no pg_hba.conf entry for host "3.70.201.172", user "surabi", database "bpsimple"

Please tell what to do?

regards
surabhi