Notes: 23 Networking, Word Game

Topic: Networking & Internet

Every computer on the internet has an IP address
The Internet Protocol delivers packets to IP addresses
IPv4 packets are limited to 64kB
In practice, they are frequently limited to ~1.2kB because that’s the limit on Ethernet
IP packets are unreliable - they may or may not actually get to their destitionation
Transmission Control Protocol builds reliable streams on top of IP packets
- You open a connection
- Either side can send and recieve arbitrary sized chunks of data
- Data is delivered reliably and in order.
How?
- Send a packet, reply with a confirmation, resend or send the next packet
- That’s too slow
- Window:
  - Send the next 10 packets
  - Send an array of 10 confirmations
  - Resend any missed packets, send any new packets in the shifted 10 packet window
HTTP builds sending “files” on top of TCP
- GET /index.html HTTP/1.0
- 200 OK/n/n<html …
- GET /logo.png HTTP/1.0
- 200 OK/n/nPNG bytes…
Websockets tunnels streams “on top” of HTTP…

Word Game

https://words.homework.quest/

Game model.

Sample Code


/**
 * Interact with sample word list.
 *
 * @author Nat Tuck
 */
public class Words {
    /**
     * Read sample word list.
     *
     * @return  List of words
     */
    static List<String> readWords() {
        try {
            InputStream raw = App.class
                .getResourceAsStream("/words.txt.gz");
            GZIPInputStream unz = new GZIPInputStream(raw);
            InputStreamReader rdr = new InputStreamReader(unz);
            BufferedReader buf = new BufferedReader(rdr);
            return buf.lines().toList();
        }
        catch (Exception ee) {
            throw new RuntimeException("read failed");
        }
    }

    static List<String> randomWords(int nn) {
        var words = readWords();
        var ys = new ArrayList<String>();

        while (ys.size() < nn) {
            var ww = pickRandom(words);
            if (!ys.contains(ww)) {
                ys.add(ww);
            }
        }

        return ys;
    }

    static <T> T pickRandom(List<T> xs) {
        int ii = (int)(xs.size() * Math.random());
        return xs.get(ii);
    }
}

package demo;

import java.io.Console;

public class App {
    static Game game;
    static int turn;
    static int points;
    static Console con;

    public static void main(String[] args) {
        game = new Game();
        turn = 1;
        points = 0;
        con = System.console();

        while (!game.gameOver()) {
            con.printf("\n\n == Turn %d, Points %d ==\n", turn, points);
            con.printf("%s\n\n", game.view());

            con.printf("Guess a non-vowel.\n");
            int cc = readLetter();

            int count = game.addGuess(cc);
            con.printf("found %d letters\n", count);
            if (!isVowel(cc)) {
                points += count;
            }

            turn++;
        }
    }

    public static int readLetter() {
        while (true) {
            var line = con.readLine("letter? ");
            if (line.length() > 0) {
                return line.codePointAt(0);
            }
        }
    }
}

package demo;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class Game {
    final List<String> words;
    Set<Integer> guesses;
    int points;

    Game() {
        words = Words.randomWords(6);
        guesses = new TreeSet<Integer>();
        points = 0;
    }

    String view() {
        var xs = words.stream().map((ww) -> wordView(ww)).toList();
        return String.join(" ", xs);
    }

    String wordView(String word) {
        var yy = new StringBuilder();
        for (var cc : word.codePoints().toArray()) {
            if (guesses.contains(cc)) {
                yy.append(Character.toString(cc));
            }
            else {
                yy.append("-");
            }
        }
        return yy.toString();
    }

    int countLetter(int cc) {
        return (int) String.join(" ", words).codePoints().filter((xx) -> xx == cc).count();
    }

    int addGuess(int cc) {
        int yy = countLetter(cc);
        guesses.add(cc);
        return yy;
    }

    int countUnknown() {
        return (int) view().codePoints().filter((cc) -> cc == '-').count();
    }

    boolean gameOver() {
        return countUnknown() == 0;
    }
}

package demo;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class Game {
    final List<String> words;
    Set<Integer> guesses;
    int points;

    Game() {
        words = Words.randomWords(6);
        guesses = new TreeSet<Integer>();
        points = 0;
    }

    String view() {
        var xs = words.stream().map((ww) -> wordView(ww)).toList();
        return String.join(" ", xs);
    }

    String wordView(String word) {
        var yy = new StringBuilder();
        for (var cc : word.codePoints().toArray()) {
            if (guesses.contains(cc)) {
                yy.append(Character.toString(cc));
            }
            else {
                yy.append("-");
            }
        }
        return yy.toString();
    }

    int countLetter(int cc) {
        return (int) String.join(" ", words).codePoints().filter((xx) -> xx == cc).count();
    }

    int addGuess(int cc) {
        int yy = countLetter(cc);
        guesses.add(cc);
        return yy;
    }

    int countUnknown() {
        return (int) view().codePoints().filter((cc) -> cc == '-').count();
    }

    boolean gameOver() {
        return countUnknown() == 0;
    }
}