CMSC 417 Computer Networks Spring 2009
Programming Assignment 1
Assigned: 02/05/2009 Due: 02/12/2009, 11:59:59 PM.
1 Introduction
In this assignmentyouwill writetheserver programwhichwill communicateusingsocketswiththeclient
programin thepreviousassignment.
2 The Protocol
Your server will run on the linuxlab cluster machines andwill listen onaTCPsocket boundtoaportas
described below.Notethatyoucannotbindtoaportbelow1024withouthavingsuperuser (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 server program must
workwithany port, but when you are testing yourserver programyoushould only use theportsyouhave
been allocated to avoid collision with others.
The rest of the protocol is as described in Assignment 0.
3 The server program
Thecommandlinesyntaxforaminimalserver is given below.Theserver will taketheportnumber asan
argument. If the port number is not specified, the server will listen to SERVER PORT instead.
server [<port>]
•The cookies should be generated randomly, in the range from 1 to 1000 (inclusive).
•After successfulcommunications(i.e., all messages areexchanged correctly accordingtotheprotocol),
the server MUST print the client’s login ID, last name, the two cookies it generates, client’s IP address
and port number, and the comment. All the information must be in a single line. An example:
cs417001 Huang 564 383 128.8.126.208:48542 See you later!
•Note well: your server should not accept spurious input from the clients.
•Wewill test yourserver withnon-conformingclients; theserver should printoutanerrormessage
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 theconnectionwhen it findsabadmessagefromtheclient.Badmessages, as
per assignment 0, are ones that have an incorrect magic string, incorrect message type or too many
fields, etc. Remember, you also have to check whether the sum of cookies in client’s BYE message is
correct.
•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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