How do I start writing an MMO game server?

Question

I am developing a multi-player on-line game.

I just started coding the server but I have no idea how to do it. Do I have to use threads ?

And if i do, do I need one thread for every client?

Knowing that I am using UDP, can I use multiple sockets in different threads to send packets on the same port?

edit:

server does:

-listen for client connections

-when a client connects:

    -update files (send new files to the client)

    -retrieve data from database

    -loop to retrieve and update live data

-when client disconnects:

    -update data in database

Answer 1

I may be wrong, but your question makes it seem like you are missing a lot of knowledge in order to successfully write an MMO server. I know this message will likely fall on deaf ears because I was in your position when I started programming.

My answer: If I were you I would start smaller. If you want to learn to write an MMO server I would do the following.

• Write a TCP based p2p chat client.
• Extend that chat client to work with NAT routers
• Extend the chat client to have a central server that authenticates and stores message history
• Extend it to have a secure handshake with the server to verify the client software and server software/location
• Write a high level architecture of what you would want your MMO server to be
• Read some articles on MMO server architectures
• Start expanding your high level architecture into more and more detail
• Write essential user stories for your architecture
• start implementing your server

The answer you probably want:

• Write a thread for the listener to accept incoming connections using TCP
• Once the player is connected, use TCP for chat messages and sector changes
• Use UDP for in-sector movement
• Each connection gets its own thread for the messaging
• UDP can be implemented with threads (if you really want) but I would probably use some sort of queue on one thread that accepts movement messages. Or spread it out depending on how many connections you get.