Synchronizing Online MySQL and Local MySQL db

[Molson31]

I've got a new project which involves using a local MySQL database, something I've never had to do. What I need to accomplish is having a very typical online MySQL database that can communicate with another MySQL database on a local machine.

 

This is what the flow chart would look like.

 

Local PC <--> Local MySQL DB <--> Internet <--> Online MySQL DB <--> Website

 

The local PC will only occasionally be online, to POST and GET new information to and from the Online MySQL DB.

 

My questions are:

Does the Local DB need a third-party application to POST and GET from the online DB?

Does the Local PC have to be a server? Ie does MySQL need to be a service?

I have learned about master-master replication but someone told me the Local PC would always have to be online, which I disagree; it could just poll occasionally. But I need to understand how a Local MySQL DB works; how can it connect to one on the web?

 

Thanks and I hope this makes sense.