Sunderban is located at a distance of around 120 km from Kolkata. The closest railway station to the entry point of Sunderban is Canning and you can catch one of the many suburban trains running from Kolkata to Canning. From there you can travel by road to Godkhali Port and board a boat that will take you to the Sunderbans.
You can also hire a private vehicle to reach the Godkhali Port from Kolkata via SH 3.