I see there is a hole located below the 2nd or 3rd window. What is its purpose?

(Sources: flickr.com and planespotters.net)
I see there is a hole located below the 2nd or 3rd window. What is its purpose?

(Sources: flickr.com and planespotters.net)
Static ports. (capt & FO).
For sensing static (atmospheric) pressure ultimately used by various flight instruments (such as airspeed indicator, altimeter, etc.)

(Source: b737.org.uk)