When making ODBC remote connection, which executable is called?

Hello,

After I install PostgreSQL to Windows Server 2008, I cannot connect to
it through another computer.  I believe the Window's firewall is
blocking the traffic.

So I go to the firewall setup to create a new "Inbound" rule.  When
creating a "Custom-type" rule to specify the details, I have the
following question.

I can specify the rule applies to "PostreSQL" service.  But I am not
certain what program it should be applied to?  Is it:
      - "[PostgreSQL_install_dir]\bin\postgres.exe" or other file?

Many thanks!

Nim