Description
This assignment has the following goals:
1. To solidify your understanding of IPC principles.
2. To develop greater appreciation for the different IPC mechanisms.
3. To gain hands-on experience using shared memory.
4. To gain hands-on experience using message queues.
5. To gain hands-on experience using signals.
6. To learn how to combine shared memory and message queues in order to
implement a practical application where the sender process sends information
to the receiver process.
Overview
In this assignment you will use your knowledge of shared memory and message queues in
order to implement an application which synchronously transfers files between two
processes.
You shall implement two related programs: a sender program and the receiver program as
described below:
• sender: this program shall implement the process that sends filesto the receiver process.
It shall perform the following sequence of steps:
1. The sender shall be invoked as ./sender file.txt where sender is the name of the
executable and file.txt is the name of the file to transfer.
2. The program shall then attach to the shared memory segment, and connect to the
message queue both previously set up by the receiver.
3. Read a predefined number of bytes from the specified file, and store these bytes in
the chunk of shared memory.
4. Send a message to the receiver (using a message queue). The message shall contain a
field called size indicating how many bytes were read from the file.
5. Wait on the message queue to receive a message from the receiver confirming successful reception and saving of data to the file by the receiver.
6. Go back to step 3. Repeat until the whole file has been read.
7. When the end of the file is reached, send a message to the receiver with the size
field set to 0. This will signal to the receiver that the sender will send no more.
8. Close the file, detach shared memory, and exit.
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• receiver: this program shall implement the process that receives files from the sender
process. It shall perform the following sequence of steps:
1. The program shall be invoked as ./recv where recv is the name of the executable.
2. The program shall setup a chunk of shared memory and a message queue.
3. The program shall wait on a message queue to receive a message from the sender
program. When the message is received, the message shall contain a field called
size denoting the number of bytes the sender has saved in the shared memory
chunk.
4. If size is not 0, then the receiver reads size number of bytes from shared
memory, saves them to the file (always called recvfile), sends message to the
sender acknowl- edging successful reception and saving of data, and finally goes
back to step 3.
5. Otherwise, if size field is 0, then the program closes the file, detaches the shared
memory, deallocates shared memory and message queues, and exits.
• When user presses Control-C in order to terminate the receiver, the receivershall deallocate memory and the message queue and then exit. This can be implemented by
setting up a signal handler for the SIGINT signal. Sample file illustrating how to do
this have been provided (signaldemo.cpp).
Technical Details
The skeleton codes for sender and receiver can be found on Titanium. The files are as
follows:
• sender.cpp:the skeleton code for the sender (see the TODO: comments in order to
find out what to fill in)
• recv.cpp: the skeleton code for the receiver (see the TODO: comments in order to find
out what to fill in).
• msg.h: the header file used by both the sender and the receiver
It containsthe struct of the message relayed through message queues). The struct
containstwo fields:
– long mtype: represents the message type.
– int size: the number of bytes written to the shared memory.
In addition to the structure, msg.h defines macros representing two different message
types:
– SENDER_DATA_TYPE: macro representing the message sent from sender to
receiver. It’s type is 1.
– RECV_DONE_TYPE: macro representing the message sent from receiver to
the sender acknowledging successful reception and saving of data.
• NOTE: both message types have the same structure. The difference is how the
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mtype field is set. Also, the messages of type RECV_DONE_TYPE d o not make
use of the size field.
• Makefile: enables you to build both sender and receiver by simply typing make at
the command line.
• signaldemo.cpp: a program illustrating how to install a signal handler for SIGSTP
signal sent to the process when user presses Control-C.
Please note: by default the skeleton programs will give you errors when you
run them. This is because they are accessing unallocated, unattached regions of
shared memory. It’s your job to fill in the appropriate functionality in the
skeleton, de-noted by the TODO comments, in order to make the programs
work.
The following links provide additional documentation aboutshared memory and message
queues:
• Message Queues: http://beej.us/guide/bgipc/output/html/multipage/mq.html
• Shared Memory: http://beej.us/guide/bgipc/output/html/multipage/shm.html
Bonus
Implement separate versions of sender and receiver which instead of relying on message
queues to signal events,rely purely on signals. Hint: use handlers for SIGUSR1 and
SIGUSR2. Hint: how can you tell the receiver the number of bytesin the shared memory?
Submission Guidelines:
• This assignment MUST be completed using C or C++ on Linux.
• You may work in groups of 3.
• Please hand in your source code electronically (do not submit .o or executable code)
• You must make sure that the code compiles and runs correctly.
• Write a README file (text file, do not submit a .doc file) which contains
– Your Section#, Name and Email Address.
– The programming language you used (i.e. C or C++).
– How to execute your program.
– Whether you implemented the extra credit.
– Anything special about your submission that we should take note of.
• Place all your files under one directory with a unique name (such as p2-[userid] for
assignment 2, e.g. p2-ytian).
• Tar the contents ofthis directory using the following command.tar cvf [directory
name].tar
[directory name] E.g. tar -cvf p2-ytian.tar p2-ytian/
• Use TITANIUM to upload the tared file you created above.
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Grading Guideline:
• Program compiles: 10’
• Correct use of message queues: 30’
• Correct use of shared memory: 30’
• Program deallocates shared memory and message queues after exiting: 10’.
• Correct file transfer: 10’
• Correct signal handling: 5’
• All system calls are error-checked: 5’
• README file: 5’
• Bonus: 10’
• Late submissions shall be penalized 10%. No assignments shall be accepted after 24 hours.
Academic Honesty:
Academic Honesty: All forms of cheating shall be treated with utmost seriousness. You
may discuss the problems with other students, however, you must write your OWN
codes and solutions. Discussing solutions to the problem is NOT acceptable (unless
specified otherwise). Copying an assignment from another student or allowing another
student to copy your work may lead to an automatic F for this course. Moss shall
be used to detect plagiarism in programming assignments. If you have any questions about
whether an act of collaborationmay be treated as academic dishonesty, p l e a s e consult the
instructor before you collaborate. Details posted at
http://www.fullerton.edu/senate/documents/PDF/300/UPS300-021.pdf.
