Programmierprojekt/documents/docs/networking/commands/protocol-document.md

Protocol Document

This document describes the protocol for client-server communication in our application. It defines the structure of requests and responses, the supported commands along with thier request parameters, response formats and possible errors.

Table of Contents

• Protocol Document
• Table of Contents
• General structure of requests
• Preconditions
  • Parsing
    • Error Response
  • Command dispatching
    • Error Response
  • Command parsing
    • Error Response
• Pre executions checks
• Commands

General structure of requests

As mentioned before, our protocol is based on POP3. Each command is represented as a single line of text, starting with the command name followed by parameters. The server responds with a status line indicating success or failure, followed by the body.

Requests can have parameters that provide additional information for the command. Parameters are key-value pairs separated by a equal sign (=).

Responses are collections of key-value pairs, containing either a value or another collection, allowing for nested structures. Each collection is ended with the END keyword.

Preconditions

The serverside pipeline to process incomming requests consists of multiple stages. Each of these stages can yield an error response if the request does not meet the requirements of that stage.

Parsing

One of these stages is the parsing. It is responsible for parsing the raw request into a structured format that can be easily processed by the command handlers. It validates the syntax of the request aswell.

Error Response

Code	Discription
PARSING_ERROR	The body of the request contains syntax errors (see message field of response for more details)

Command dispatching

After the request has been successfully parsed, the next stage is to dispatch the PrimitiveRequest to the appropriate CommandParser. This is done by the CommandDispatcherDispatcher, which uses the command name to determine which parser to use.

Error Response

Code	Discription
UNKNOWN_COMMAND	The command is unknown to this server. No parser has been defined

Command parsing

Once the PrimitiveRequest has been dispatched to the appropriate CommandParser, the parser is responsible for parsing the parameters of the request and creating a Request that can be executed by the responsible CommandHandler.

Error Response

Code	Discription
MISSING_PARAMETER	A required parameter is missing from the request (see message field of response for more details)

Pre executions checks

Pre-execution checks are reusable validation steps that can be registered on command handlers. They are implemented as HandlerCheck instances and are executed by the CommandHandlerExecutor before the handler's main logic is invoked.

Commands

Commands are the core of our protocol, representing the various actions that clients can request from the server. Each command has a unique name and may require specific parameters in addition to pre-execution checks. The server processes these commands and responds accordingly.