The variable IP_PORT is a string, which should be in the form of: IP address in front, port number in the back, colon: separated in the middle.

Take out the IP address and port number in this string through these two sentences respectively.

Awk divides the string IP_PORT into two fields by -F ":"and specifies the delimiter as a colon.

Print $ 1 prints the first field, which is the IP address.

Print $2 prints the second field, the port number.