CMSC 417 Computer Networks Fall 2007
Programming Assignment 1
Assigned: Sep. 18 Due: Sep. 25, 11:59:59 PM.
1 Introduction
In this assignment you will write the server program which will communicate using sockets with the client
program in the previous assignment.
2 The Protocol
Your server will run on the linuxlab cluster machines and will listen on a TCP socket bound to a port as
described below. Note that you cannot bind to a port below 1024 without having superuser (root) acccss.
Given that your class account login id is cs4170xx, the ports you should use are 10xx0-10xx9 (inclusive).
Thus, if your login id is cs417060, you will use port range 10600-10609. Your final project must work with
any port, but when you are testing your project you should only use the ports you have been allocated to
avoid collision with others.
The rest of the protocol is as described in Project 0.
3 The server program
The command line syntax for a minimal server is given below. The server will take the host name and port
as arguments (you can re-use the argument parsing code in the client).
server [<hostname>[ <port>]]
•The cookie should be generated using the formula:
(a+b+c+d)×13 mod 1111, where 0 ≤a, b, c, d ≤255 and a.b.c.d is the IP address of the
client.
•After the successful communication, the server MUST print the cookie it generates along with the
client’s login id, first name, IP address and port number. All this information should be in a single
line. An example is:
555 cs417000 Kan-Leung from 128.8.126.208:48542
•Note well: your server should not accept spurious input from the clients.
•We will test your server with non-conforming clients; the server should print out an error message
containing the client’s IP address and port number also in a single line, as such:
**Error** from 128.8.126.133:48522
and immediately close the connection when it finds a bad message from the client. Bad messages, as
per project 0, are ones that have an incorrect magic string, incorrect message type or too many fields.
Remember, the cookie sent in the STATUS message has to match the cookie in the CLIENT BYE
message for a communication to be successful.
•Do NOT print out any other debugging messages. They are useful for you, but not for your TA to
grade.
•All output should be printed to stdout.
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