Each time player has 7 moves to do ,create your tree upon those possible movments ,each has grading for its preferablility (one movement to win +50,two movement to win +15,three movement to win+5,forenemysamecalculation*-1.8).Usingalphabetapruningtake thesuitablemovement.
http://web.mit.edu/sp.268/www/2010/connectFourSlides.pdf?fbclid=IwAR0 -oi2_-ujM2hgyDV6Umq5o51qvyCt_BuXhH_Sgkgr518ACuKIQgzmQoSY https://www.youtube.com/watch?feature=youtu.be&v=y7AKtWGOPAE&fbclid=I wAR1jmbifHQxpKIf8iUKg6nrStMOy4-Bue-BfnpFwrJ45qsnByepTpt-dAqo&app=desk top