Homework 1, Sockets Solution

Goal



You can develop a distributed application, i.e. define tasks, assign tasks to processes and develop an application-specific communication protocol for process interaction using TCP or/and UDP sockets.



You can develop an object-oriented node of a distributed application with a simple but yet informative and responsive (graphical) user interface, taking into account communication latency in a distributed application.
You can use concurrent threads in nodes of a distributed application in order to im-prove scalability and performance (e.g. response time), and to hide communication latency.



2 Grading




The grading is as follows:




Not accepted Your work has not been accepted, and you have no score.




0 points Your work has been accepted.




1 point Your work has been accepted before or on due date.




2 points Your work has been accepted before or on due date. Also, it has an acceptable layered architecture and is well designed. This means it follows the guidelines of the lecture on architecture, and of the programming examples on the course web.




3 Auto-Generated Code and Copying




You must be able to explain and motivate every single part of your code. You are not allowed to copy entire files or classes from the example programs on the course web, even if you understand it and/or change it. However, you are allowed to write code which is very similar to the example programs on the course web. You are also allowed to use GUI builders and other tools that generate code.










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Network Programming, ID1212 Homework 1, Sockets







4 Tasks




You are to solve one of the following two tasks. You do not get any extra points from solving both.




Task 1, The Hangman Game




Develop a client-server distributed application in Java for the "Hangman" word guessing game (described in Wikipedia at https://en.wikipedia.org/wiki/Hangman_(game)). As a source of words, you can use the file words.txt on the course web.




Rules of The Game




Table 1 shows a sample execution of the game. In brief, the game is played as follows. The server chooses a word from a dictionary, and the client (the player) tries to guess the chosen word by suggesting letters occurring in the word (one letter at a time), or by suggesting the whole word. The client is only allowed as many failed attempts as there are letters in the word. A failed attempt is a suggestion of a letter not occurring in the word, or of the wrong word. If the client suggests a letter that occurs in the word, the server places the letter in all its positions in the word; otherwise the number of allowed failed attempts is decreased by one. At any time the client is allowed to guess the whole word. The client wins when the word is completed using single letters, or the whole word is guessed correctly. The client loses when the counter of allowed failed attempts reaches zero.




The client is able to play multiple such games, and the server records the total score. The score is initially zero, if the client wins the score is increased by one, if the client loses the score is decreased by one. This means the score can be negative.




Requirements on Your Program




All of the following requirements must be met in order for your solution to be accepted.




Client and server must communicate by sending messages over a TCP connection, using blocking TCP sockets.



The client must not store any data. All data entered by the user must be sent to the server for processing, and all data displayed to the user must be received from the server.



The client must have a responsive user interface, which means it must be mul-tithreaded. The user must be able to give commands, for example to quit the program, even if the client is waiting for a message from the server.



The server must be able to handle multiple clients playing concurrently, which means it must be multithreaded.















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The user interface must be informative. The current state of the program must be clear to the user, and the user must understand what to do next.



User’s action
User interface shows
Word chosen by
server












Remain-






Word
ing failed
Score






attempts




Connect to server
no value
no value
0
no word chosen
Start game
_______
7
0
hangman
guess p
_______
6
0
hangman
guess a
_a___a_
6
0
hangman
guess m
_a__ma_
6
0
hangman
guess t
_a__ma_
5
0
hangman
guess gangman
_a__ma_
4
0
hangman
guess hangman
hangman
no value
1
no word chosen
Start game
___
3
1
dog
guess a
___
2
1
dog
guess e
___
1
1
dog
guess n
___
0
0
no word chosen






Table 1: A sample execution of the client-server hangman game.







What is NOT Required of Your Program




Below is an explanation of things that do not affect your score.




Minor changes or misunderstandings of the rules are allowed, as long as your pro-gram does not become notably simpler than a program implementing the correct rules.



Your are not required to create a graphical user interface. A command line UI is sufficient.



Task 2, The Rock-Paper-Scissors Game




Develop a distributed peer-to-peer application for the multi-player rock-paper-scissors game. (Wikipedia page at https://en.wikipedia.org/wiki/Rock-paper-scissors).




Rules of The Game




Each player runs a node with a user interface that allows to play the game and show scores. Table 2 shows a sample execution of a game with three nodes. In a round of the










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game, each player chooses one of rock, scissors, or paper. Then the nodes communicate their choices to each other in order to compare the choices to see who won. Rock wins over scissors, scissors wins over paper, and paper wins over rock. Points are awarded as follows. Assume n 1 players. Award m players (n - m) points each if they choose the same gesture and beat the other (n - m) players. This rule implies that if all n players choose the same gesture (i.e. if m = n), points are not awarded. If a player beats all the others (i.e. if m = 1), the winner is awarded (n - 1) points. When a round is over, the players may decide to play another round or to quit the game. The user interface must reflect the score of the last round and the total score.




Requirements on Your Program




All of the following requirements must be met in order for your solution to be accepted.




Nodes must communicate by sending messages over TCP or UDP, using blocking sockets. Note that you may face problems running UDP multicast over KTHOPEN or Eduroam. Therefore, you are advised not to use multicast.



Use only one peer node for each player, do not use an additional coordinator node. Each node must run exactly the same program, there may not be any “master” node.



Your program must allow at least three nodes to participate in the game.



The node must have a responsive user interface, which means it must be mul-tithreaded. The user must be able to give commands, for example to quit the program, even if the node is waiting for a message from another node.



The user interface must be informative. The current state of the program must be clear to the user, and the user must understand what to do next.






What is NOT Required of Your Program




Below is an explanation of things that do not affect your score.




Minor changes or misunderstandings of the rules are allowed, as long as your pro-gram does not become notably simpler than a program implementing the correct rules.



Your are not required to create a graphical user interface. A command line UI is sufficient.



























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Network Programming, ID1212 Homework 1, Sockets










User A’s
User B’s
User C’s
User A’s
User B’s
User C’s
action
action
action
view
view
view
start




round: 0
none
none
game




total: 0








start
round: 0
none
round: 0




game
total: 0


total: 0


start


round: 0
round: 0
round: 0


game


total: 0
total: 0
total: 0


rock


round: 0
round: 0
round: 0






total: 0
total: 0
total: 0
paper




round: 0
round: 0
round: 0






total: 0
total: 0
total: 0




paper
round: 1
round: 0
round: 1






total: 1
total: 0
total: 1




paper
round: 0
round: 0
round: 0






total: 1
total: 0
total: 1


scissors


round: 0
round: 0
round: 0






total: 1
total: 0
total: 1
paper




round: 0
round: 2
round: 0






total: 1
total: 2
total: 1
rock




round: 0
round: 0
round: 0






total: 1
total: 2
total: 1




rock
round: 0
round: 0
round: 0






total: 1
total: 2
total: 1


rock


round: 0
round: 0
round: 0






total: 1
total: 2
total: 1






Table 2: A sample execution of the peer-to-peer rock-paper-scissors game with three play-ers.





































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