Essam, 24, returns for his second permanent spell with the Whites having captained the club back in 2014-15 and played 15 games on loan last year.
The centre-back was released by Eastleigh last month after one year with the Spitfires.
Former Gillingham trainee Essam has also played for Crawley, Dartford, Woking and Luton Town.
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Connor Essam has joined Dover Athletic on a two-year deal following a loan spell last season from Eastleigh.