svcpy: server to server copy

a basic server-to-server copy application.

on a single binary, it can be a server or a client.

example usage:

• on the server side: ./svcpy -listen=:4321 -path=/srv/ftp
• on the client side ./svcpy -connect=1.2.3.4:4321 -path=/mnt/backups/ftp

notes:

• prevent information leak by taking diff on the server side
• general flow:
  • server starts to listen at port
  • client connects
  • client generates a file-list (local)
  • client sends #-of-files to the server
  • server reads #-of-files from the client
  • client sends filelist as json to the server
  • server reads filelist from the client
  • server generates a diff from the list received and what it has locally
  • server verifies diff in terms of file counts
  • server creates tar archive and pushes to socket
  • client reads the tar archive and unpacks to path specified

todo:

• add some kind of authentication (token, openid etc)
• generate filelist in deferred fashion.
  • eg: checksums should be async (much like python's yield keyword)
• add compression (gzip/xz) to speed up transfer
• add bandwidth limitation