CE150 Course Project

Spring 2003

FTP Server/Client

The aim of this project is to get more understanding of client/server programming in C. In this project, you will be implementing a simple TCP based FTP server and client program. Your implementation must be in C using the BSD sockets. Your server and client program should be designed to run on UNIX machines of CATS. The specifications for the server and client side are as follows:

Server Specifications

Your server must authenticate logins from clients using a password (which could be hardcoded).
Your server must use a port number specified as the second command line parameter.
Your server must be a concurrent server and should handle multiple clients at the same time.
Your server should be designed to start by typing the command,
```
    myftpd dir_name port_number
```
Where dir_name is the name of the default directory which will be displayed when a client is connected and port_number is the port number for the server to listen. Whenever your server receives a connection request from a client, the server should ask the client for a password. The connection must be terminated with an error message (Authentication Failure), if the password does not match the expected password. On successful authentication the client should be greeted with a Success message followed by an ftp prompt.

Client Specifications

The client should be designed to start by typing the command,

  myftp server_name port_number

Where server_name is the name or ip address of the server and port_number is the port where the FTP server is running. This should be followed by password authentication.

The following commands should be available in the ftp prompt:

```
myftp> ls
```
No arguments. To display directory listing in the remote server.
```
myftp> lls
```
No arguments. To display directory listing in the local machine.
```
myftp> pwd 
```
No arguments. To display current directory name in the remote server.
```
myftp> lpwd 
```
No arguments. To display current directory name in the local machine.
```
myftp> cd remote-path 
```
Change directory in the remote server.
```
myftp> lcd local-path 
```
Change directory in the local machine.
```
myftp> get remote-file [local-file] 
```
Get the file 'remote-file' from the remote server to the local machine with name 'local-file' (if specified in the command line else it should be same as the remote file name).
```
myftp> put local-file [remote-file] 
```
Transfer local-file to the remote server.
```
myftp> exit 
```
Exit the connection.
```
myftp> help 
```
List all the available commands with a short description.

All these commands when executed should return a Success/Failure status. All the path names and file names should be considered relative to the current directory (unless absolute path name is given). After a successful file transfer, a success message should be displayed with the number of bytes transferred (Optionally you could display status for ongoing transfers by some means).

Submission Instructions

You will be submitting the following files:

Source Code for client and server.
Makefile to generate binaries (The name of the binary must be 'myftp' for the client and 'myftpd' for the server).
README - A text file containing information about all the submitted files. Description of known problems or errors. Any special comments about the project (like what you learned, what you had trouble with etc.,).
NOTE: We will be using the CATS homework submission system to receive and test the project. Precise submission instruction will be updated to this web page when they are finalized.

Grading Policy

Your server and client programs will be tested using automated scripts to make sure it works properly. The source code should be commented and readable. We look for the following in your submission:

Working as per the specification.
Programming style and comments.
Memory leaks, stale sockets and zombie process WILL decrease your score.

Full credit will be awarded only if all the requirements are met. If your server/client fails the tests in the automated scripts, partial credits might be given depending on the error.

Notes

Before starting to code your program, it is advisable to design the client-server protocol (like the messages to be exchanged, the sequence of the message exchanges, termination condition etc.,)
For reading directories or file structure from C program, check the man pages for opendir(), readdir(), dirent(), stat/lstat/fstat(), closedir().
Be careful with socket handling and sending messages through the sockets. YOUR PROGRAM SHOULD NEVER DO BROADCASTING. All the connections should be closed properly when the program is terminated.
Do not leave any stale connections (check using netstat -ap or sockstat). Do not leave any zombie processes (Check using "ps -aux | grep "your_user_id", a status Z indicates zombie process). Your program should not have any memory leaks.

Resources

UNIX Network Programming, Volume 1, Second Edition: Networking APIs: Sockets and XTI, Prentice Hall, 1998.
Beej's Tutorial
TCP/IP FAQ
Socket Programming FAQ
C Programming FAQ

Contact Venkatesh (venkat@soe.ucsc.edu).