The many uses this blog


I was reviewing last year's posts and I realized that many of the posts are applicable now as we are going through the same chapters at the same time. So instead of reposting the same entries I invite you to check last year's entries along the whole course and there you'll find useful information, interesting links and related material.

Please note that assignments are different.

Class attendance record

These are the attendance numbers so far (out of 13 classes).





















Ayoub10

Aitor13

Martin9

Luis Manuel8

Edgar10

Carlos8

Erol1

Ramazan12

Jakub1

Roberto2

Ana6

Manuel6

Javier11

Taha9

Carlos S1


Please note that some of you are joining the class quite late. I understand that you may have other subjects too, but please note you'll need some effort to catch up with the class.

Sample IM server application

I've created a server application like the one you have to write for assignment #1.

You'll find it running on port 7777 on the IP address 158.42.53.17. If for some reason it is not accepting your connections, please let me now, as a power outage might have happened on my side and manual restart would be needed.

Please note that the messages about a new client entering the server or a client leaving the server are not required on your code. I've just added them to give users a bit more of information.

News and reminders

Since Nov 16th we will be back to the "Seminari Nord" room. I've just posted the text of the first assignment, and I want to remind you that --although it is optional work-- doing it right will be worth 5 out of 100 points.

You do the four scheduled assignments right and you already have 20% of the subject.

You come to all the classes and you have 10% more.

Still not enough to pass the subject (you need 50%) but closer ...

Just a word of warning: Assignments are personal work, not team work. Your code will be checked against all the other submitters. If a copy is found all the involved parties will score 0% no questions asked. It is in your best interest to keep your work for yourself.

As with any other doubts you may have about the subject, I'm available during office hours for helping you solving them.

Programming Assignment #1

Instant Messaging Server

Your job is to write a Java application that will act as a the server for an Instant Messaging application. Clients will connect to the server [using a TCP connection] to talk to each other. Clients will type messages that are composed of one or more lines of text. Each time a user types a new line of text at the keyboard, that line will be transmitted to the server.

Each time the server receives a new line from any client, it will send a copy to all the clients but the one who sent it (i.e. to prevent a confusing double echo on the sending-client side).

Any client that wants to abandon the service MUST type a line with the text QUIT. Whenever the server receives such a line of text it will interpret its meaning, closing the socket this client was using. From them on, no attempt to send any more data to that client will happen (note: trying to send data to an already closed socket would trigger an exception).

Still, a client could leave the service by just closing the connection without the mandatory QUIT command. You do not need to manage that case though.

Your Code

Your code has to conduct the following tasks:

  1. Accept any number of simultaneous clients, but it is safe to assume no more than one hundred simultaneous clients.

  2. Retransmit any text line, including empty lines, to any active client but the one typing that text line.

  3. Not to retransmit those lines which only contents is the QUIT command. Any combination of upper and lower case characters should be accepted and recognized (i.e: both QuiT and quit should work too).

  4. The server program prints “NEW CLIENT” whenever a new client connects to the server and it prints “CLIENT GONE” when any client quits the system.

Some tips

  • Server listens on port 7777

  • You may use several telnet windows as clients of your server (for testing purposes) by just typing;

telnet localhost 7777

Due date

Your Java source code has to be submitted by email (address available on the front page) by Nov 30th.

If you have any doubt about the assignment I strongly suggest you to stop by my office during office hours (posted on the web).

News


I mentioned in the class this sample server program.

Next class will be held on Aula Informática, on the ground level, see the plane (click on the image to get a larger view).

A bird's eye view of the Internet


There are several projects aimed to provide such a view. This is just one of them.

A tree is built connecting lower level networks. As you can see a huge hierarchical view is shown, and that is just part of how it was the Internet some time ago as it is evolving on a daily basis.

Changing location

During the two first weeks of November we will have our classes in the "Aula Informática" so all of you can try for yourself with a networked computer how things really work. This will be from November the 2nd till November 10th.

FYI: For Your Information

Any submission to the IETF intended by the Contributor for publication as all or part of an IETF Internet-Draft or RFC and any statement made within the context of an IETF activity is considered an "IETF Contribution". Such statements include oral statements in IETF sessions, as well as written and electronic communications made at any time or place, which are addressed to:
  • the IETF plenary session,
  • any IETF working group or portion thereof,
  • the IESG, or any member thereof on behalf of the IESG,
  • the IAB or any member thereof on behalf of the IAB,
  • any IETF mailing list, including the IETF list itself, any working group or design team list, or any other list functioning under IETF auspices,
  • the RFC Editor or the Internet-Drafts function

All IETF Contributions are subject to the rules of RFC 3978 and RFC 3979.

Statements made outside of an IETF session, mailing list or other function, that are clearly not intended to be input to an IETF activity, group or function, are not IETF Contributions in the context of this notice.

Please consult RFC 3978 for details.

Welcome to all of you

I've just returned from a trip to a Finish university and I've discovered there are thrity eight people enrolled on the subject this year. This is definitely our best score ever and I just hope most of you will actually stick to the English group (I'm afraid that some of you might have ended in this group because other groups are full).

I'll see you all on Thursday,

Miguel

September news

I am glad to inform you that Rami passed the subject.

Antonio:
I'm glad to see you again enrolled in the subject. You are welcome to come to the class too, work permiting.

Still reading this blog?

Well, maybe you failed the subject, sorry.

On the other hand, if you are planning joining us next course, please be welcome and feel free stoping by my office (I'll be out of town week 38th though).

There is just another opportunity for you to take an exam next September 14th, Thursday, at 16:00.

Best of luck (not that I think it has lots to do with the outcome),

Dr. Sanchez

Solved Exam

It is here.

Please contact me if you want to have a look at your exam. Marks will be final in a few days.

What not to do this summer


This list contains some of the IP ranges that you better avoid if you do not want a free trip to Guantanamo or another sunny place with the latest fashion in orange suits.

Subject's marks

Several students did not show up at the exams and they have no marks:
ANTONIO, ALBERTO, JOSE LUIS and RAMON

The rest of you, brave people, did get the following results:

NAME EXAM LAB ASSIG. ATT. TOTAL COURSE_MARK
-------------- ---- --- ------ ---- ------- -----------
DIEGO 44 35 1 20 53.05 63.25
JORGE 62 70 0 0 64.60 67.29
TOMASZ 70 70 2 17 83.39 82.85
IGNACIO 62 45 1 17 71.49 79.05
LUISMANUEL 22 0 0 2 20.67 28.73
VLADISLAV 82 55 1 21 90.23 86.24
RAMI 38 0 0 2 36.37 21.15

Congratulations on your results. Unfortunately those below the 50% course mark have failed the subject, please remember we will have another exam in September covering THE WHOLE SUBJECT (assignments or lab exam are not available in September).

Your exam is available for you to check your results (just email me for a revision slot). In a few days I'll post the 2nd term exam answered.

Wold Cup telnet fun

I've just learned that some people are using the old and aged telnet application for new uses:

                                   _ajjaa                             
_Q???4Qf
_,...,_ ) a/]QQb
.'@/~~~\@'. jQQba
//~~\___/~~\\ _, .?QQ#[ _
|@\__/@@@\__/@| ]m _.7 "asLaas_a/
|@/ \@@@/ \@| , ,\J#L -!4Wba
\\__/~~~\__// [aL[ \ \jmm jP
'.@\___/@.' ,b#'"[ \jmmmmm _P.
`"""""` a##' "4P#mmm# _ya
_P !4####m ?]aa/
/' aaJ#U###m# 4QP'
' aa,/4!44! '
jf _'jQQQQyb7b /
'. '.QQQQ4QQPb )?
QQQ'QQP?' jg/ f
_yQP']QQb aa
a#W?'..QQQQ?)? ?'
"##' _jQQP'
.j? [ jQQ'
aJ jmaaX#L???
? am'
_QjQQQ/
)QQQP?
4QQQ/

So try any of these live-streams based on telnet:

telnet ascii-wm.net 2006

MIRRORS:

telnet diego.ascii-wm.net 2006
telnet pinguin.eikon2.fs.ei.tum.de 2006

Warning: Exam ahead


As a reminder: Written exam will be held on June 23rd at 4:00pm. You either have to do the second term exam if you passed the first term or a final exam covering first and second terms if you didn't.

If you have attended to all the lab sessions please remember you are eligible for a written laboratory test, to be held afterwards (same day). Any score you get there will only add to your total score (it is my way of telling you should do it if you are eligible).

Those who fail the subject will have an exam in September covering all the subject.

Remember the final grade will include the marks from you class attendance and the assignments you turned in.

Till the exam, I'll be available to address any of your questions on my office hours (Mon & Tue 9:00 - 12:00).

Encryption ... rap?


Rapper MC Plus+ has created a song titled "Alice and Bob" based on the improbable theme of computer cryptography. It is freely available online. I'm not sure this will become a huge hit but, who knows?

New software threats

As I mention in the last class, I read this post where new types of malware activity are commented. While I am not afraid this will have a wide effect it is a new twist as to how some people can turn out a benefit from creating this particular type of sofware.

Last assignment is out

This last assignment is about finding the best route in a graph. This is part of what a routing algorithm does. Actually, a routing algorithm will search for all the best routes to all the destinations.