How to replicate or synchronize when databases can't have a direct connection with each other?

I have a central webservice over the internet which gets different information from different softwares and stores them in a Sql server 2008R2 database.

In addition to webservice some windows applications exist in different cities which all of them have local databses.

Now I wanna have replication between these local databases and the central database. but t开发者_高级运维here is no any direct connection as like as "VPN" between local databases and central database.

so how can I do something like replication or synchronization between local databases and central database over the internet.

I'm thinking about sending local databases via web service. what is your idea?

My local databases are Sql server 2000 version

How about log shipping? You can even use FTP (FTPS--FTP over SSL, for security) to send the logs to be later on applied to the central DB. Since you have SQL 2000, you'd have to restore data to a copy of the DB in "restore" mode and then merge with central DB using SQL.

Also, from personal experience--if setting VPN is costly, you can consider using SSH. Free implementations for Windows exist, and they do a good job for secure file copy, just like FTPS.

I wouldn't use a webservice for this purpose, especially if the amount of data is large.