File Transfer Protocol

0 Introduction

In this client-server project, a client can request a file or a set of files from the server. The server searches for the file/s in its file directory rooted at its ~ and returns the tar.gz of the file/files requested to the client (or an appropriate message otherwise). Multiple clients can connect to the server from different machines and can request file/s as per the commands listed in section 2.

The server, the mirror and the client processes run on different machines and communicate using sockets only.

1 Server

The server and an identical copy of the server called the mirror [see section 3] both run before any of the client (s) run and both of them wait for request/s from client/s

Upon receiving a connection request from a client, the server forks a child process that services the client request exclusively in a function called processclient() and (the server) returns to listening to requests from other clients.

The processclient() function enters an infinite loop waiting for the client to send a command

Upon the receipt of a command from the client, processclient() performs the action required to process the command as per the requirements listed in section 2 and returns the result to the client

Upon the receipt of quit from the client, processclient() exits.

For each client request, the server forks a separate process with the processclient() function to service the request and then go back to listening to requests from other clients

2 Client

The client process runs an infinite loop waiting for the user to enter one of the commands.

Note: The commands are not Linux commands and are defined(in this project) to denote the action to be performed by the server.

Once the command is entered, the client verifies the syntax of the command and if it is okay, sends the command to the server, else it prints an appropriate error message.

List of Client Commands:

findfile filename

If the file filename is found in its file directory tree rooted at ~, the server returns the filename, size(in bytes), and date created to the client and the client prints the received information on its terminal.

Note: if the file with the same name exists in multiple folders in the directory tree rooted at ~, the server sends information pertaining to the first successful search/match of filename

Else the client prints “File not found”

Ex: $ findfile sample.txt

sgetfiles size1 size2 <-u>

The server returns to the client temp.tar.gz that contains all the files in the directory tree rooted at its ~ whose file-size in bytes is >= size1 and <= size2

size1 <= size2 (size1 >= 0 and size2 >= 0)

-u unzip temp.tar.gz in the pwd of the client

Ex: $ sgetfiles 1240 12450 -u

dgetfiles date1 date2 <-u>

The server returns to the client temp.tar.gz that contains all the files in the directory tree rooted at ~ whose date of creation is >= date1 and <= date2 (date1 <= date2)

-u unzip temp.tar.gz in the pwd of the client

Ex: $ dgetfiles 2023-01-16 2023-03-04 -u

getfiles file1 file2 file3 file4 file5 file6 <-u>

The server searchs the files (file 1 ..up to file6) in its directory tree rooted at ~ and return temp.tar.gz that contains at least one (or more of the listed files) if they are present.

If none of the files are present, the server sends “No file found” to the client (which is then printed on the client terminal by the client)

-u unzip temp.tar.gz in the pwd of the client

Ex: $ getfiles new.txt ex1.c ex4.pdf

gettargz <extension list> <-u> //up to 6 different file types

The server returns temp.tar.gz that contains all the files in its directory tree rooted at ~ belonging to the file type/s listed in the extension list, else the server sends the message “No file found” to the client (which is printed on the client terminal by the client)

-u unzip temp.tar.gz in the pwd of client

The extension list has at least one file type and can have up to six different file types

Ex: $ gettargz c txt pdf

quit

The command is transferred to the server and the client process is terminated.

3 Mirror

The server and the mirror (the server’s copy possibly with a few additions/changes) are to run on two different machines/terminals.

The first 4 client connections are to be handled by the server.

The next 4 client connections are to be handled by the mirror.

The remaining client connections are to be handled by the server and the mirror in an alternating manner- (ex: connection 9 is to be handled by the server, connection 10 by the mirror, and so on)