cmsc 417 programming assignment one
January 31, 2008
Your task in this assignment will be to write a single program that first acts as a multicast sender and
then a multicast listener.
This assignment is to be done individually.
1 Context
Over the rest of the semester, we will build a virtual network using a combination of multicast frames (to
emulate multi-access networks) and unicast tunnels to emulate a backbone network.
Building this application blends networked application development with simulations of network pro-
tocols, so you should be able to build both network protocols and network applications at the end of the
semester.
2 Deadline
DUE: Feb 15. Take note! This is only approximately 120 lines of C code.
3 Requirements
The program should do two things in exactly the order below.
•First, send a message to a multicast address, specified below.
•Next, print all messages received at the multicast address until the process is interrupted (control-c).
4 Message format
Your message header should consist of the following:
uint8_t version; /* set to 1; if you receive anything else, discard. */
uint8_t ttl; /* set to 1; if you receive anything else, it’s fine. */
uint16_t payload_length; /* bytes following the header, not including trailing null of a c string */
uint32_t account_identifier; /* digits of your account name: unsigned int i; sscanf("cs417xxx", "cs417%u", &i); htonl(i); */
uint32_t source_address; /* unused for now, set to 0 and ignore. */
uint32_t destination_address; /* unused for now, set to 0 and ignore. */
uint16_t checksum /* unused for now, set to 0 and ignore. */
uint16_t protocol /* must be 1; if you receive anything else, discard. */
•The types used above can be found in:
#include <inttypes.h>
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