#Synchronous plain text editor

WARNING: this program has NO safety measures in place. Data is transmitted and stored as UTF-8 plain text, including passwords. Please, don't use this.

#Plainsync server

The recommended way of setting up the server is using Docker. The image can be built and run by issuing docker-compose up -d in the project's root. Alternatively, simply launch the server with python3 ps_server.py.

#Configuration

Configuration is done through command line options (see python ps_server.py --help) or environment variables, with CLI options taking precedence. The storage location directory will be automatically created if it does not exist, other locations must be available for the server to start.

Environment variables:

• PLAINSYNC_HOST: host name for the server, default localhost
• PLAINSYNC_PORT: port number to use, default 9999
• PLAINSYNC_STORAGE: location of the data storage, default $PWD/data
• PLAINSYNC_DATABASE: location of the database, default $PLAINSYNC_STORAGE/plainsync.sqlite
• PLAINSYNC_LOGLEVEL: log level for the server, default INFO
• PLAINSYNC_LOGFILE: location of the log file, default is standard output

#Server operation

The server is built using the socketserver module from Python's standard library. The server listens on specified socket and relegates new connections to instances of TCPHandler class, which establish sessions and handle further request.

Every connection is expected to first provide an AuthRequest, which is then verified and, upon success, given a session ID. The handler then answers incoming requests and ends the session after the connection is aborted, or if the incoming message cannot be parsed.

Information about available users, their files and file shares is stored in an sqlite database, which is accessed by the TCPHandler using an instance of DatabaseManager. Users must be manually added to the database, for example using the sqlite command line client. Files themselves are stored under PLAINSYNC_STORAGE and identified by their unique ID.

#Plainsync client

You can run client directly from terminal with command python ps_client.py. Once opened, you can log in by typing login and password. In the main window, on the left side you can see your files. First column contains names of files you own and files shared with you. Next columns contain information such as: date of creation, date of last edit and recent editor.

#Options available

As a user, you can use this options:

• Open file - Selected file will be downloaded from server and open. You can modify the file, changes will be send to server if you save the file.
• New file - New file will be created.
• Delte file - Selected file will be deleted from the server. If you try to delete file, that is shared to you by other user you will no longer have acces to this file. File will not be deleted from the server, but only from your shared files.
• Share - You can share your file with other user.
• Delte share - You can stop sharing your file.
• Close - You will be log out and the application will get closed.

#Client backed

Performing every operation, the client will send a specific request to the server. If the request is sent correctly and the response doesn't contain any error, the result of the operation will be shown on the screen. If any error occurs, it will be shown on the screen and the operation will be aborted. Available requests are described inside the request.py file.

#Protocol details

The protocol makes use of Python's ability to deconstruct objects into dictionaries, which can then be serialized into JSON strings and sent via a TCP connection. Upon receiving the message can be reconstructed into an object, making it clear which attributes a message should and should not possess.

Each functionality has its own Request object, with the servers possible Response types specified in its docstring. Messages are sent over TCP with a 2-byte proto-header, which specifies the length of the JSON message. The entire payload is pictured below.

  2 bytes of message length as 16-bit unsigned integer in "big indian" byteorder
  │
  ▼
┌─────────┬──────────────────────────────────────────────────┐
│ ███████ │ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ │
└─────────┴──────────────────────────────────────────────────┘
           ▲
           │
           JSON message encoded with UTF-8

The common/transfer.py module provides helper functions for sending and receiving messages in the manner described above.