A Simple TCP Server Programming Exercise

The Task

Write a simple TCP server that listens on some port and calculates the MD5 sum of the data received, returning it as a hex-encoded string.

Assuming your server is listening on port 7000, we can test it using the netcat command-line utility:

$ echo -n 'Hello, MD5 server!' | nc localhost 7000
ba6f4fdbbfad6e8613f4f9459db93c7e

And we can verify if it is correct by comparing it with a command-line md5 utility:

$ SERV_OUT=$(echo -n 'Hello, MD5 server!' | nc localhost 7000)
$ echo $SERV_OUT
ba6f4fdbbfad6e8613f4f9459db93c7e
$ CLI_OUT=$(echo -n 'Hello, MD5 server!' | md5)
$ echo $CLI_OUT
ba6f4fdbbfad6e8613f4f9459db93c7e
$ [ $SERV_OUT = $CLI_OUT ] && echo "Great, our MD5 server seems to be working"
Great, our MD5 server seems to be working

Evaluation Criteria

Firstly, the code has to be correct. But working code is only the first step in any program.

Some other criteria can be:

• Reliability. What happens if things fail?
• Simplicity. See "Reliability" above.
• Performance. What happens if we put your server under load?

It is basically up to you to implement a solution that shows off your skill level and what you believe is good code.