CMSC 417 - Project Hot News

PROJECT NEWS

CMSC 417 (section 0201, f97)

You do not need to link -lnsl on Alpha

The C library (/usr/lib/libc.a) that is automatically included in a link request contains the network related libraries.

How to submit projects

Tar all source code files, Makefile and typescript file (no object or executables):

>tar cvf prog1.tar *

Submit it using the submit program residing in ~aus02:

>~aus02/submit 1 prog1.tar

The general form is

>~aus02/submit <assignment-number>
                    <file-to-submit>

Use lowercase letters for the command line request type

Please write your programs to use lowercase letters for the command line request type argument as lowercase letters is what I will be using to test your program.
Example: client host addr somewhere.cs.umd.edu
(NOT client host ADDR somewhere.cs.umd.edu)

A small correction to Socket Handout

near line 48: memset((void *) &server, sizeof server) should have a second argument of zero.

Socket debugging tools

There isn't much available on Unix other than netstat.

Examine the exit codes of all your system calls (bind, unbind, etc). These are very helpful at diagnostics.

A common mistake is to apply a host-to-net (or net-to-host) conversion on a "anyhost" address (as in receivefrom any host). This converts the "anyhost" address to a specific host address.

Port numbers

If your account is ausN, then use ports in the range 5000+10*N to 5000+10*(N+1)-1 for your socket binding. (Of course, port numbers chosen by the system may not be in this range.)

Class newsgroup

Newsgroup csd.cmsc417 is available for both sections of CMSC 417. Currently accessible from aitsAlpha cluster, csd, and glue.

Port numbers

If your account is ausN, then use ports in the range 5000+10*N to 5000+10*(N+1)-1 for your socket binding. (Of course, port numbers chosen by the system may not be in this range.)

You should use g++ to compile

Even if you programmed in C, you should use g++ to compile your project 2 or you will likely get an error in /usr/include/c_asm.h

READ THIS: Format for submission of project 2

The Tar file you submit should only have the following files (with exactly these names):
[m|M]akefile
queue.h
queue.[c|C]
driver.[c|C]
typescript
README

The Tar file should not be a tarred directory with the files inside it. Nothing (error messages,extraneous info) should be printed out in queue.c Make sure to use the -Wall option (the comment in the header file will not be counted against you).
Points will be deducted if you do not follow these guidelines.

Project 2 information

You will need to link in the pthreads libarary. To do this, add "-lpthread" to the end of your (g++) compile line.
The manual page on the pthread_cond_timedwait() function is particularly helpful--read it.
You should use the function pthread_get_expiration_np() to convert the time passed as a parameter in your dequeue function into a time understandable by the pthread_cond_timedwait() function.

Acceptable warnings for Project 2

"/usr/include/pdsc.h:506: warning: `/*' within comment" will not have points taken off for it.
"/usr/bin/ld: Warning: clog defined as GLOBAL DATA but is defined in a shared lib as a GLOBAL FUNC" will not have points taken off for it. This warning can be avoided by not including iostream.h in your queue.c file (and there should be no reason to include it in any case).
"ANSI C++ forbids implicit conversion from `void *' in argument passing" warning will not have points taken off. To eliminate the warning, try the following for thread function and call:
```
  void * threadFunction( void * param )  
  pthread-create( ..., threadFunction, ... )
```
There should be no other warnings.

Some clarifications for Term Project

Use the UNREACHABLE return code for the AAL7 connect call if the remote server is listening but not accepting.
The AAL7_disconnect is a "graceful" close (as in TCP closing). It should use timeouts to prevent half dead connections (i.e. when the connection close ack is lost).
To identify AAL7 message types (e.g. conn req, connect ack, accept ack, etc), you can use (a) the three unused bits in the last word of the AAL7 trailer, or (b) some other bits in the trailer, or (c) introduce fields in the "data" part of AAL7 packets. You will probably want to use the AAL7 trailer since it has its own loss probability with the garbler.

How do I get a 53 byte packet?

Bit pack the VPI, CVI, PT, and CLP fields into 4 bytes. Create a char array of 49 bytes. One byte can hold the checksum field. Even though the sizeof function will specify 56 bytes, pass a size of 53 to the garbler, and everything should work.

Term Project Schedule for Section 0201

Oct 28 (Tues) Submit draft of design proposal.
Nov 11 (Tues) Submit final version of design document.
Nov 12 (Wed) Demonstration of status of implementation. During TA office hours. This is now optional.
Dec 11-12 (Th-Fri) Final projcet demonstration, ... (same date as section 0101).