added BudaClientServerStuff, an example for some client server functionality.

Übung/BudaServerClientStuff/.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

Übung/BudaServerClientStuff/.idea/misc.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="true" project-jdk-name="11" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

Übung/BudaServerClientStuff/.idea/modules.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/BudaServerClientStuff.iml" filepath="$PROJECT_DIR$/BudaServerClientStuff.iml" />
+    </modules>
+  </component>
+</project>

Übung/BudaServerClientStuff/BudaServerClientStuff.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

Übung/BudaServerClientStuff/README.txt

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+This is a demo of some (very basic) client / server functionality.
+Run BudaClient.java for the Client and BudaServer.java for the Server. Everything connects locally via port 8090
+
+Type "Name:Jonas B." to change the client's name to Jonas B (the "." is where the name stops).
+
+Type "Names" for the Server to display everyone who is connected along with their name (if they have set a name).
+
+Typing "Quitx" should quit everything but I havent quite managed to implement that yet so just repeatedly use ctrl+c to quit everything.
+
+-Jonas

Übung/BudaServerClientStuff/src/BudaClient.java

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+
+import java.io.*;
+import java.net.Socket;
+
+public class BudaClient {
+    public static void main(String[] args) {
+        Socket sock = null;
+        try {
+            sock = new Socket("localhost", 8090);
+            OutputStream out= sock.getOutputStream();
+            BufferedReader conin = new BufferedReader(new InputStreamReader(System.in));
+            String line = "";
+            while (true) {
+                line = conin.readLine();
+                out.write(line.getBytes());
+                if (line.equalsIgnoreCase("Quitx")) {
+                    break;
+                }
+                //line.startsWith() //todo: automatically handle name lengths
+                //TODO: Implement inputStream in.
+            }
+
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+}

Übung/BudaServerClientStuff/src/BudaClientThread.java

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+
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.Socket;
+
+public class BudaClientThread implements Runnable {
+    int number;
+    Socket socket;
+    String name;
+
+
+    public BudaClientThread(int number, Socket socket) {
+        this.number = number;
+        this.socket = socket;
+        name = "";
+    }
+
+    public void run() {
+        System.out.println("Connection " + number + " established.");
+        try {
+            InputStream in = socket.getInputStream();
+            OutputStream out = socket.getOutputStream();
+            byte[] command;
+            String comString;
+            while (true) {
+                command = new byte[5];
+                System.out.println("Waiting to receive a line");
+                in.read(command);
+                System.out.println("Got a line!");
+                comString = new String(command);
+                System.out.println("Client number " + number + " sent this message: " + comString);
+                if (comString.equalsIgnoreCase("Quitx")) {
+                    BudaServer.quit = true;
+                    System.out.println("I just set quit to true!");
+                    break;
+                }
+
+                //todo: do as switch.
+
+                if (comString.equalsIgnoreCase("NAME:")) { //todo: implement these as methods?
+                    setName(in);
+                }
+
+                if (comString.equalsIgnoreCase("NAMES")) {
+                    printnames();
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void printnames() {
+        for (BudaClientThread t: BudaServer.Clients) {
+            System.out.println(t.name + " connected (#" + t.number + ")");
+        }
+    }
+
+    public void setName(InputStream in) throws IOException {
+        //byte[] namebyte = new byte[0];
+        String nameString = "";
+        int i;
+        while (true) {
+            i = in.read();
+            if (i == 46) break;
+            nameString = nameString + (char) i;
+        }
+        this.name = nameString;
+    }
+
+}

Übung/BudaServerClientStuff/src/BudaServer.java

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+
+
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.HashSet;
+
+public class BudaServer {
+    public static boolean quit = false; //todo: meaningfully implement this
+    public static HashSet<BudaClientThread> Clients = new HashSet<BudaClientThread>();
+    static int connections = 0;
+
+    public static void main(String[] args) {
+        ServerConnector ServC = new ServerConnector();
+        Thread ServCThread = new Thread(ServC);
+        ServCThread.start();
+        System.out.println("Server has entered its main loop");
+        while (!quit) {
+            //Main server stuff goes here
+        }
+        //ServCThread.stop(); //todo: find some alternative for this.
+        System.out.println("stopping the main BudaServer thread.");
+        System.out.println("Quitting after the next connection is made.");
+    }
+}

Übung/BudaServerClientStuff/src/ClientListener.java

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+import java.io.*;
+import java.net.Socket;
+
+public class ClientListener implements Runnable{
+    private final Socket sock;
+
+    public ClientListener(Socket sock) {
+        this.sock = sock;
+    }
+
+    public void run(){
+        byte[] command = new byte[5];
+        String comString;
+
+        try {
+            InputStream in = sock.getInputStream();
+            in.read(command);
+            System.out.println("Got a line!");
+            comString = new String(command);
+        } catch (IOException e) {
+            e.printStackTrace();
+
+        }
+    }
+}

Übung/BudaServerClientStuff/src/ServerConnector.java

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+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+public class ServerConnector implements Runnable{
+    public void run() {
+        try {
+            System.out.println(
+                    "Warte auf Verbindungen auf Port 8090...");
+            ServerSocket servSock = new ServerSocket(8090);
+            while (true) {
+                Socket socket = servSock.accept();
+                System.out.println("got a connection: socket " + BudaServer.connections + socket.toString());
+                BudaClientThread newClientThread = new BudaClientThread(++BudaServer.connections, socket);
+                BudaServer.Clients.add(newClientThread);
+                Thread bCT = new Thread(newClientThread);
+                bCT.start();
+            }
+        } catch (IOException e) {
+            System.out.println("server got an error");
+            System.err.println(e);
+            System.exit(1);
+        }
+
+
+    }
+}