mmo-project/fortran/server/README.md

server

The server implementation is as simple as I could make it.

I found a library called mod_dill from the tcp-client-server demo code from a book on modern fortran. This gave me a simple TCP interface to send and recieve "messages".

Originally I had tried saving formatted fortran data into a string and trying to send that, but when you convert the fortran string to a c-string it oftend became garbled and unusable when sent through the tcp connection so I stopped using that method.

I found in fpm official registry a json library which would make it much easier to deal with data transfer.

The simplest way to implement the communcation between the server and clients would be a series of tcp requests and responses.

• request

  • int :: request_type
    • ping # 0
    • login # 1
    • logout # 2
    • move # 3
  • str(24) :: username
  • double :: x_pos
  • double :: y_pos

• response

  • array :: records
    • str(24) :: username
    • str(24) :: color
    • double :: x_pos
    • double :: y_pos

For each request, the same response is returned with is a list of the logged in users.

The commands that can be sent to the server are logging in, logging out, moving, and the default "ping" which is essentially a noop from the servers pov.

The server uses the same sqlite library as the www implementation.

The server loop is:

1. listen for connection
2. read message from client
3. convert c string to fortran string
4. convert the fortran string to a json object
5. run the command from the json object
6. create a json array of the logged in users and send to client.