FTPImplementation

An implementation of FTP protocol, including client & server.

Introduction

Steps to establish the connection:

1. client send USER to server
2. client send PASS to server
3. logged in if username & password are valid.

Control socket & Data socket

1. control socket: used for commands transferring
2. data socket: used for data transferring

Data Transfer Mode: PASV

1. client send PASV to client
2. server will return its ip address & port
3. socket for data transferring establishs with specified ip & port
4. data socket will be reestablished for each data transferring