Exercise 2: Building Reliable File Transfer – Part 1

In this C exercise you will implement reliable file transfer between a client and a server (from the client to the server) using TCP (in part 1) and using UDP (in part 2).

Introduction:

This exercise is composed of two parts. In the first part, you will implement a client/server which transfer files from the client to the server using TCP. In the second part, we will implement the same file transfer using UDP.

Synopsis:

For running the server:

srftp server-port 

For running the client:

crftp server-port  server-hostname filename-to-transfer

server-port:                 is the port used by the server
server-hostname:        is the host name of the server
filename-to-transfer:   is the name of the file to transfer from the client to the server, it must reside in the same directory as the client was executed from.
    It will be copied to the same directory as the server was executed from with the same name as it had on the client. If such a file already exists on the server then it should be overwritten.

Basic requirements of the server design:

• The server should handle clients using a single process, using the select() system call.
• Remember that on the next exercise, we will change the underlying protocol to UDP so try to think about future implementation as well.

Basic requirements of the client design:

• The client initiates the file transfer

Testing Your Program:

• Run the server on one machine. Run the client and send a file to the server. Use “diff” command to verify the file was created properly, and has the same size.

Error Handling:

• You can assume the input parameters are correct.
• In case of an unrecoverable error (e.g., if  the program can't open a socket), the program must exit(1) and write an error to STDERR. In case of success the client program should return 0.

Useful system calls:

socket, bind, connect, listen, accept, send, recv, select, close, inet_addr, htons, ntohs, gethostbyname

What to submit

• The files srftp.c and crftp.c.
• A Makefile which compiles the executables
  ctftp and srftp (should work on the system Linux computers like inferno)
• A README
• Example Makefile is found here
• Example c files : crftp.c srftp.c
• Don't forget to check your tar using the checkme_ex2a.sh script.