How to Sync Data Between Computers (PostgreSQL)

Question

I need to synchronize data between databases from different computers using postgresql. I am not refering to database replication.

 

This is the scenario, we deployed a desktop application (C# using postgresql). We have a user of 5 field staffs. Everytime they go out from the office, they bring their laptop (desktop application installed with postgre). Once they are back to the office, they need to synchronize their (5 staffs) data to the main server (postgresql) 

 

How can I do that? New to pg-sql. Thanks for any help or can point me to a right path.