What is post code for monaghan town?

I come from Monaghan and generally there are no post codes or as they say in America zip codes, usually if you were sending a letter from another country to Ireland it would look like this : John Doe
10 Park street
Co. Monaghan
Republic , Ireland

And the letter finds its way there. Now if you were to send the letter to a residence in the country where there is no house numbers it would look like this :

John Doe
Stranooden
Co. Monaghan
Republic , Ireland

The local postman just knows all the residence and the mail makes its way to you with out post codes or zip codes.