He joined Eastleigh from Basingstoke Town, scoring 20 goals in 41 games during the 2017-18 season and two in 11 appearances in the 2018-19 campaign.
Before that Smart made 32 appearances and scored 12 goals for hometown club Horndean between 2015 and 2017.
Smart began a football education scholarship with Portsmouth aged 16, which earned him a full scholarship to attend the University of Fort Lauderdale in Florida.
But his stint in American was only a month long before he returned to the south coast.
Smart has previously had trials at Sheffield Wednesday and Sunderland, and attracted interest from several clubs before Eastleigh signed him.
He scored once in 29 league appearances in his first season at Eastleigh and then twice in 42 league games in the 2020-21 campaign.
Last season he scored twice in 26 games for The Spitfires, playing against Halifax home and away, but also had a loan spell at Havant and Waterlooville.
Smart is Town's second signing of the summer after the capture of midfielder Jack Hunter from Gateshead.