add tcp server and client chapter

Sascha Schulz

2024-09-30 bd8f799af4fd6d61a5cef8b4faa6789fcb5e2b76

 index.html

@@ -4239,6 +4239,132 @@
                     </code>
                  </pre>
               </section>
               <section>
                  <h3>Kryptographie</h3>
               </section>
               <section>
                  Mithilfe des nativen <code>crypto</code>-Moduls ist es möglich, moderne sichere kryptografische Verfahren zu verwenden:
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        const crypto = require("crypto");
                     </code>
                  </pre>
                  Hierzu nutzt NodeJS selber die weit verbreitete OpenSSL-Bibliothek
               </section>
               <section>
                  Einen MD5-Hash erzeugen:
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        const crypto = require("crypto");

                        const hash = crypto.createHash("md5");
                        const md5 = hash.update("abcdefg")
                           .digest(); // Buffer (default)
                           // .digest("hex") // Hexadezimal
                           // .digest("utf8") // Bytes forciert als Chars
								
                        console.log(md5);
                     </code>
                  </pre>
               </section>
               <section>
                  <p>Aufgabe</p>
                  <p>Erzeuge jeweils den md5- und den sha256-Hash als Hex-Wert der beiden Texte in der Datei <code>text-examples.txt</code> und vergleiche jeweils ihren md5- und sha256-Hash miteinander</p>
               </section>
               <section>
                  <h3>Zippen</h3>
               </section>
               <section>
                  Mit dem nativen Modul <code>zlib</code> ist es möglich, Kompression in seinen Anwendungen zu nutzen.
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        const zlib = require("zlib");

                        // Komprimieren
                        zlib.deflate("abc" /* buffer | string */, (err, compressed) => {});
								
                        // Dekomprimieren
                        zlib.inflate(compressed /* buffer */, (err, decompressed) => {});
								
                        // Als Stream
                        const zipper = zlib.createDeflate();
                        const unzipper = zlib.createInflate();
								
                        source.pipe(zipper).pipe(target);
                        source.pipe(unzipper).pipe(target);
                     </code>
                  </pre>
               </section>
               <section>
                  <p>Aufgabe</p>
                  <p>Nutze die einfachen Varianten <code>zlib.deflate</code> und <code>zlib.inflate</code>, um einen beliebigen Text zu komprimieren und anschließend wieder zu dekomprimieren</p>
               </section>
               <section>
                  <p>Aufgabe</p>
                  <p>Nutze die Stream-Varianten <code>zlib.createDeflate</code> und <code>zlib.createInflate</code>, um jeweils ein getrenntes Programm für die Kompression und Dekompression mit <code>process.stdin</code> und <code>process.stdout</code> zu machen, sodass in der Konsole folgende Nutzung möglich ist:</p>
                  <pre>
                     <code class="bash" data-trim data-line-numbers>
                        echo "abc" | node compress.js | node decompress.js
                        cat file.txt | node compress.js > file.zipped
                        cat file.zipped | node decompress.js > file.txt
                     </code>
                  </pre>
               </section>
               <section>
                  <h3>TCP-Verbindungen</h3>
               </section>
               <section>
                  <ul>
                     <li>Bidirektionale Verbindung</li>
                     <li>Duplexfähig</li>
                     <li>Besteht immer aus Server- und Client-Socket</li>
                  </ul>
               </section>
               <section>
                  Mit dem nativen Modul <code>net</code> ist es möglich, eine TCP-Verbindung aufzubauen
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        /* Server */
                        const net = require("net");

                        const server = net.createServer((socket) => {
								
                           // new incoming connection
                           socket.on("data", (data) => {
                              // data is a buffer
                           });
								
                           socket.write("Hello World!");
                        });
								
                        server.listen(3000);
                     </code>
                  </pre>
               </section>
               <section>
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        /* Client */
                        const net = require("net");

                        const socket = net.connect(3000, () => {
                           // 'connect' listener
                        });
								
                        socket.on("data", (data) => {
                           // data is a buffer
                        });
                     </code>
                  </pre>
               </section>
               <section>
                  <p>Aufgabe</p>
                  <p>Implementiere die Clientlogik in der <code>tcp-client.js</code>, um dem Server ein <code>"Hello Server!"</code> zurück zu senden</p>
               </section>
               <section>
                  <p>Aufgabe</p>
                  <p>Sende eine festgelegte Datei vom Server zum Client. Der Server liest die Datei ein und sendet die Inhalte zum Client, welcher diese wiederum in eine Zieldatei schreibt. Eventuell darf auch noch eine Kompression mittels Zip / Deflate implementiert werden.</p>
               </section>
            </section>
         </div>
      </div>