Homework 1: A command-line email client

Create a program, hw1.c, and a matching Makefile to build the hw1 binary.

The program takes a variable number of file names as command line arguments, thus:

./hw1 jakob.txt hamed.txt alexis.txt

Each file contains an email to be sent, formatted like a simplified raw email (try ‘view source’ on any email of yours).

From: Busy Beaver <beaver@busy.com>
To: Jakob Eriksson <jakob@uic.edu>
Subject: Give me an A

My program sends email. Thus, I deserve an A.

The parts above the blank line are headers that are interpreted differently for display by an email client, the part below is the email text body.

Your program should deliver the email in each file to its intended recipient, by contacting the recipient’s incoming email server. Which email server to contact depends on the destination address of the email. You may assume there is only one destination address in each email file.

Resolving MX DNS records

There are several ways to find the incoming mail server for a given domain, but they all come back to the domain’s MX record in the DNS. We will study DNS in great detail later in the class. For now, use the “popen()” function run the command “host -t MX”.

Sending the email

To send the email, your program connects to the receiving server using a network socket. See “man socket” and “man connect” for API specifics. The exchange proceeds by SMTP (https://tools.ietf.org/html/rfc821) (anno 1982). Note that modern email servers generally require addresses to be on the form “Full Name <user@domain>” rather than simply “user@domain”.

Turn-in

Your turn-in consists of two files: hw1.c and Makefile. We will grade your program by typing “make hw1”, then running it with several example email files. If the program does not make, we will not grade it. Do not include binaries in your turn-in.

Homework turn-in will be by github classroom. Here is the invitation link.

After you have turned in your submission, please double-check you were successful by cloning the repository again, and typing “make hw1” in the submission folder.