#include <arpa/inet.h>

  -- Function: int inet_pton (int AF, const char *CP, void *BUF)
      This function converts an Internet address (either IPv4 or IPv6)
      from presentation (textual) to network (binary) format.  AF should
      be either `AF_INET' or `AF_INET6', as appropriate for the type of
      address being converted.  CP is a pointer to the input string, and
      BUF is a pointer to a buffer for the result.  It is the caller's
      responsibility to make sure the buffer is large enough.

struct in6_addr output;
char* input;

// READ THE INPUTSTRING INTO INPUT

if(inet_pton(AF_INET6, input, &output)) //Parse input to a binary IPv6 address in output.
{
  perror(0);
  exit(1);
}; 
// use your binary IPv6 address called output