inet_ntoa()
converts a in_addr
to string:
The inet_ntoa function converts an (Ipv4) Internet network address into an ASCII string in Internet standard dotted-decimal format.
inet_addr()
does the reverse job
The inet_addr function converts a string containing an IPv4 dotted-decimal address into a proper address for the IN_ADDR structure
PS this the first result googling "in_addr to string"!