On the surface, the Serpent Gang has three leaders, but they all oversee operations from the headquarters. In Jiangdu City, control is divided among the Eight Hall Masters, and under the Hall Masters, small leaders lead gang members to manage territories and handle affairs.
The Serpent Gang's legitimate business includes maritime trade and controlling Jiangdu City's fishing market. Every fisherman who rents a boat for fishing operates under the Serpent Gang's monopoly.
In one word:
If your work involves fish, then you serve the Serpent Gang.
Beneath the surface, their operations include gambling dens and brothels.
And other unspeakable activities.
The area where Zhen Bin lives is under the control of Tiger Hall, one of the Eight Great Halls, and the culprit who broke Zhen Bin's leg is Fan Jianglong, a minor boss under Tiger Hall Master Lang Jun.
At a port dock.