CMSC 417 Computer Networks Fall 2007
Programming Assignment 0
Assigned: Sep 5th Due: Sep 12th, 11:59:59 PM.
You should use the CSIC Linux cluster systems and obtain your account information from the TA.
1 Introduction
For this assignment, you will write a client program which will communicate using sockets with
aserver program provided by us. We will give you a a sketch of the client program — all you have
to do is fill in socket-specific bits.
For each client request, our server generates and returns a random number, and then the server
and client embark on a long goodbye. Obviously, the protocol is trivial/useless, however, this
exercise will get you started on the cluster and familiarize you with sockets, network programming
and distributed debugging.
2 The Protocol
The server runs on the machine SERVER HOSTNAME and listens for requests on a TCP socket bound
to port SERVER PORT. Both constants are defined in the header file provided for you. This exercise
has four types of messages: HELLO, STATUS, CLIENT BYE and SERVER BYE. Each message
is an ASCII string, and consists of multiple fields seperated by whitespace (space (0x20) or newline
(0x0a) character). The MAXIMUM length of the string is 255.
The client initiates the protocol by sending a HELLO message to the server. The server replies
with a STATUS message. The client then sends a CLIENT BYE message, and the server terminates
the connection by sending a SERVER BYE message. A connection is successful if and only if all
of these messages are correctly sent and received. Since we are using TCP for communication in
this assignment, you do not have to worry about lost messages etc.; you only need to ensure that
all messages are sent correctly (and that you receive and parse messages correctly).
The details of each message are as follows:
•HELLO (From the client to the server: Client →Server)
The HELLO message has four fields EXACTLY in the following order
– Magic String
It MUST set to be MAGIC STRING which is a constant defined in the header file (cmsc417fall2007).
If you send a message which does not start with this magic string, the message will be
ignored.
– Message Type
The type string MUST be HELLO to indicate a message type HELLO. The server is
case-sensitive.
– Login ID
This field is your cluster login ID.
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